485BPOS

Securities Act of 1933 Registration No. 002-93601

Investment Company Act of 1940 Registration No. 811-04118

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

FORM N-1A

REGISTRATION STATEMENT UNDER THE SECURITIES ACT OF 1933 x

o Pre-Effective Amendment No.  ______

x Post-Effective Amendment No.  122

and

REGISTRATION STATEMENT UNDER THE INVESTMENT COMPANY ACT OF 1940 x

x Amendment No.  122

Fidelity Securities Fund

 (Exact Name of Registrant as Specified in Charter)

245 Summer Street, Boston, Massachusetts 02210

(Address of Principal Executive Offices)(Zip Code)

Registrant’s Telephone Number: 617-563-7000

Marc Bryant, Secretary

245 Summer Street

Boston, Massachusetts 02210

(Name and Address of Agent for Service)

It is proposed that this filing will become effective immediately upon filing pursuant to paragraph (b).

EXHIBIT INDEX

Exhibit	Exhibit No.
XBRL Instance Document	EX-101.INS
XBRL Taxonomy Extension Schema Document	EX-101.SCH
XBRL Taxonomy Extension Calculation Linkbase Document	EX-101.CAL
XBRL Taxonomy Extension Definition Linkbase Document	EX-101.DEF
XBRL Taxonomy Extension Labels Linkbase Document	EX-101.LAB
XBRL Taxonomy Extension Presentation Linkbase Document	EX-101.PRE

SIGNATURES

Pursuant to the requirements of the Securities Act of 1933 and the Investment Company Act of 1940, the Registrant certifies that it meets all of the requirements for the effectiveness of this Registration Statement pursuant to Rule 485(b) under the Securities Act of 1933 and has duly caused this Post-Effective Amendment No. 122 to the Registration Statement to be signed on its behalf by the undersigned, thereunto duly authorized, in the City of Boston, and Commonwealth of Massachusetts, on the 16th day of February 2017.

Fidelity Securities Fund

	By	/s/Stacie M. Smith
||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||		Stacie M. Smith, President

Pursuant to the requirements of the Securities Act of 1933, this Registration Statement has been signed below by the following persons in the capacities and on the dates indicated.

(Signature)		(Title)	(Date)
/s/Stacie M. Smith		President and Treasurer	February 16, 2017
Stacie M. Smith		(Principal Executive Officer)
/s/Howard J. Galligan III		Chief Financial Officer	February 16, 2017
Howard J. Galligan III		(Principal Financial Officer)
/s/Jonathan Chiel	*	Trustee	February 16, 2017
Jonathan Chiel
/s/James C. Curvey	*	Trustee	February 16, 2017
James C. Curvey
/s/Dennis J. Dirks	*	Trustee	February 16, 2017
Dennis J. Dirks
/s/Alan J. Lacy	*	Trustee	February 16, 2017
Alan J. Lacy
/s/Ned C. Lautenbach	*	Trustee	February 16, 2017
Ned C. Lautenbach
/s/Joseph Mauriello	*	Trustee	February 16, 2017
Joseph Mauriello
/s/Charles S. Morrison	*	Trustee	February 16, 2017
Charles S. Morrison
/s/Robert W. Selander	*	Trustee	February 16, 2017
Robert W. Selander
/s/Cornelia M. Small	*	Trustee	February 16, 2017
Cornelia M. Small
/s/William S. Stavropoulos	*	Trustee	February 16, 2017
William S. Stavropoulos
/s/David M. Thomas	*	Trustee	February 16, 2017
David M. Thomas

*	By:	/s/Megan C. Johnson
		Megan C. Johnson, pursuant to powers of attorney dated April 1, 2014 and October 5, 2016 and filed herewith.

POWER OF ATTORNEY

We, the undersigned Directors or Trustees, as the case may be, of the following investment companies:

Fidelity Advisor Series I Fidelity Advisor Series VIII Fidelity Beacon Street Trust Fidelity Capital Trust Fidelity Central Investment Portfolios LLC Fidelity Commonwealth Trust Fidelity Concord Street Trust Fidelity Congress Street Fund Fidelity Contrafund Fidelity Destiny Portfolios Fidelity Devonshire Trust Fidelity Exchange Fund Fidelity Financial Trust Fidelity Hanover Street Trust Fidelity Hastings Street Trust Fidelity Investment Trust Fidelity Magellan Fund Fidelity Mt. Vernon Street Trust Fidelity Puritan Trust Fidelity Securities Fund Fidelity Summer Street Trust Fidelity Trend Fund Variable Insurance Products Fund Variable Insurance Products Fund II Variable Insurance Products Fund III

in addition to any other investment company for which Fidelity Management & Research Company (“FMR”) or an affiliate acts as investment adviser and for which the undersigned individuals serve as Directors or Trustees (collectively, the “Funds”), hereby revoke all previous powers of attorney we have given to sign and otherwise act in our names and behalf in matters involving any investment company for which FMR or an affiliate acts as investment adviser and hereby constitute and appoint Thomas C. Bogle, Joseph R. Fleming, John V. O’Hanlon, Robert W. Helm, Megan C. Johnson, and Anthony H. Zacharski, each of them singly, our true and lawful attorneys-in-fact, with full power of substitution, and with full power to each of them, to sign for us and in our names in the appropriate capacities, all Registration Statements of the Funds on Form N-1A, or any successors thereto, any and all subsequent Amendments, Pre-Effective Amendments, or Post-Effective Amendments to said Registration Statements or any successors thereto, and any supplements or other instruments in connection therewith, and generally to do all such things in our names and behalf in connection therewith as said attorneys–in-fact deem necessary or appropriate, to comply with the provisions of the Securities Act of 1933 and the Investment Company Act of 1940, and all related requirements of the Securities and Exchange Commission.  We hereby ratify and confirm all that said attorneys-in-fact or their substitutes may do or cause to be done by virtue hereof.  This power of attorney is effective for all documents filed on or after April 1, 2014.

WITNESS our hands on this first day of April 2014.

/s/James C. Curvey	/s/Charles S. Morrison
James C. Curvey	Charles S. Morrison
/s/Dennis J. Dirks	/s/Robert W. Selander
Dennis J. Dirks	Robert W. Selander
/s/Alan J. Lacy	/s/Cornelia M. Small
Alan J. Lacy	Cornelia M. Small
/s/Ned C. Lautenbach	/s/William S. Stavropoulos
Ned C. Lautenbach	William S. Stavropoulos
/s/Joseph Mauriello	/s/David M. Thomas
Joseph Mauriello	David M. Thomas

POWER OF ATTORNEY

I, the undersigned Trustee of the following investment companies:

Fidelity Advisor Series VIII Fidelity Concord Street Trust Fidelity Investment Trust Fidelity Puritan Trust Fidelity Securities Fund Variable Insurance Products Fund

in addition to any other Fidelity Fund for which the undersigned individual serves as Director or Trustee (collectively, the “Funds”), hereby constitute and appoint Thomas C. Bogle, Marc R. Bryant, John V. O’Hanlon, Robert W. Helm, Megan C. Johnson, and Anthony H. Zacharski, each of them singly, my true and lawful attorneys-in-fact, with full power of substitution, and with full power to each of them, to sign for me and in my name in the appropriate capacity, all Registration Statements of the Funds on Form N-1A, or any successors thereto, any and all subsequent Amendments, Pre-Effective Amendments, or Post-Effective Amendments to said Registration Statements or any successors thereto, and any supplements or other instruments in connection therewith, and generally to do all such things in my name and behalf in connection therewith as said attorneys-in-fact deem necessary or appropriate, to comply with the provisions of the Securities Act of 1933 and the Investment Company Act of 1940, and all related requirements of the Securities and Exchange Commission.  I hereby ratify and confirm all that said attorneys-in-fact or their substitutes may do or cause to be done by virtue hereof.  This power of attorney is effective for all documents filed on or after October 5, 2016.

WITNESS my hand on this 5th day of October, 2016.

/s/Jonathan Chiel

Jonathan Chiel

XML

Label	Element	Value
Risk/Return:	rr_RiskReturnAbstract
Document Type	dei_DocumentType	485BPOS
Document Period End Date	dei_DocumentPeriodEndDate	Jan. 27, 2017
Registrant Name	dei_EntityRegistrantName	FIDELITY SECURITIES FUND
Central Index Key	dei_EntityCentralIndexKey	0000754510
Amendment Flag	dei_AmendmentFlag	false
Document Creation Date	dei_DocumentCreationDate	Jan. 27, 2017
Document Effective Date	dei_DocumentEffectiveDate	Jan. 30, 2017
Prospectus Date	rr_ProspectusDate	Jan. 30, 2017

XML

NF_Fidelity Small Cap Growth Fund_Z_PRO-01 | Fidelity® Small Cap Growth Fund

Fund Summary

Fund/Class:
Fidelity® Small Cap Growth Fund/Fidelity Advisor® Small Cap Growth Fund Z

Investment Objective

The fund seeks capital appreciation.

Fee Table

The following table describes the fees and expenses that may be incurred when you buy and hold shares of the fund.

Shareholder fees

(fees paid directly from your investment)

Shareholder Fees {- Fidelity® Small Cap Growth Fund}	NF_Fidelity Small Cap Growth Fund_Z_PRO-01 Fidelity® Small Cap Growth Fund Fidelity Small Cap Growth Fund-Class Z Equity
Redemption fee on shares held less than 90 days (as a % of amount redeemed)	1.50%

Annual Operating Expenses

(expenses that you pay each year as a % of the value of your investment)

Annual Operating Expenses {- Fidelity® Small Cap Growth Fund}	NF_Fidelity Small Cap Growth Fund_Z_PRO-01 Fidelity® Small Cap Growth Fund Fidelity Small Cap Growth Fund-Class Z Equity
Management fee (fluctuates based on the fund's performance relative to a securities market index)	0.83%
Distribution and/or Service (12b-1) fees	none
Other expenses	0.10%	[1]
Acquired fund fees and expenses	0.01%	[1]
Total annual operating expenses	0.94%

This example helps compare the cost of investing in the fund with the cost of investing in other funds.

Let's say, hypothetically, that the annual return for shares of the fund is 5% and that your shareholder fees and the annual operating expenses for shares of the fund are exactly as described in the fee table. This example illustrates the effect of fees and expenses, but is not meant to suggest actual or expected fees and expenses or returns, all of which may vary. For every $10,000 you invested, here's how much you would pay in total expenses if you sell all of your shares at the end of each time period indicated:

Sell All Shares

Expense Example {- Fidelity® Small Cap Growth Fund}	NF_Fidelity Small Cap Growth Fund_Z_PRO-01 Fidelity® Small Cap Growth Fund Fidelity Small Cap Growth Fund-Class Z Equity USD ($)
1 year	$ 96
3 years	300
5 years	520
10 years	$ 1,155

Portfolio Turnover

The fund pays transaction costs, such as commissions, when it buys and sells securities (or "turns over" its portfolio). A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when fund shares are held in a taxable account. These costs, which are not reflected in annual operating expenses or in the example, affect the fund's performance. During the most recent fiscal year, the fund's portfolio turnover rate was 143% of the average value of its portfolio.

Principal Investment Strategies

• Normally investing primarily in common stocks.

• Normally investing at least 80% of assets in securities of companies with small market capitalizations (which, for purposes of this fund, are those companies with market capitalizations similar to companies in the Russell 2000^® Index or the S&P SmallCap 600^® Index).

• Investing in companies that Fidelity Management & Research Company (FMR) believes have above-average growth potential (stocks of these companies are often called "growth" stocks).

• Investing in domestic and foreign issuers.

• Using fundamental analysis of factors such as each issuer's financial condition and industry position, as well as market and economic conditions, to select investments.

Principal Investment Risks

• Stock Market Volatility. Stock markets are volatile and can decline significantly in response to adverse issuer, political, regulatory, market, or economic developments. Different parts of the market, including different market sectors, and different types of securities can react differently to these developments.

• Foreign Exposure. Foreign markets can be more volatile than the U.S. market due to increased risks of adverse issuer, political, regulatory, market, or economic developments and can perform differently from the U.S. market.

• Issuer-Specific Changes. The value of an individual security or particular type of security can be more volatile than, and can perform differently from, the market as a whole.

• "Growth" Investing. "Growth" stocks can perform differently from the market as a whole and other types of stocks and can be more volatile than other types of stocks.

• Small Cap Investing. The value of securities of smaller, less well-known issuers can perform differently from the market as a whole and other types of stocks and can be more volatile than that of larger issuers.

An investment in the fund is not a deposit of a bank and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other government agency. You could lose money by investing in the fund.

Performance

The following information is intended to help you understand the risks of investing in the fund. The information illustrates the changes in the performance of Class I shares from year to year and compares the performance of Class I shares to the performance of a securities market index over various periods of time. The index description appears in the Additional Index Information section of the prospectus. Past performance (before and after taxes) is not an indication of future performance.

Visit institutional.fidelity.com for more recent performance information.

Performance history will be available for Class Z after Class Z has been in operation for one calendar year.

Year-by-Year Returns*

Calendar Years

During the periods shown in the chart:	Returns	Quarter ended
Highest Quarter Return	23.92%	June 30, 2009
Lowest Quarter Return	-27.62%	December 31, 2008

Average Annual Returns*

After-tax returns are calculated using the historical highest individual federal marginal income tax rates, but do not reflect the impact of state or local taxes. Actual after-tax returns may differ depending on your individual circumstances. The after-tax returns shown are not relevant if you hold your shares in a retirement account or in another tax-deferred arrangement, such as an employee benefit plan (profit sharing, 401(k), or 403(b) plan).

For the periods ended December 31, 2016

* The returns shown above are for Class I, which is not offered through this prospectus. Class Z would have substantially similar annual returns to Class I because the classes are invested in the same portfolio of securities. Class Z's returns would differ from Class I's returns to the extent that the classes do not have the same expenses.

Average Annual Total Returns{- Fidelity® Small Cap Growth Fund} - NF_Fidelity Small Cap Growth Fund_Z_PRO-01 - Fidelity® Small Cap Growth Fund	Past 1 year	Past 5 years	Past 10 years
Fidelity Small Cap Growth Fund - Class I | Return Before Taxes	11.00%	14.77%	8.48%
Fidelity Small Cap Growth Fund - Class I | After Taxes on Distributions	10.79%	12.74%	7.28%
Fidelity Small Cap Growth Fund - Class I | After Taxes on Distributions and Sales	6.39%	11.43%	6.60%
Russell 2000® Growth Index(reflects no deduction for fees, expenses, or taxes)	11.32%	13.74%	7.76%

[1] Based on estimated amounts for the current fiscal year.

XML

Label

Element

Value

Risk/Return:

rr_RiskReturnAbstract

Registrant Name

dei_EntityRegistrantName

FIDELITY SECURITIES FUND

Prospectus Date

rr_ProspectusDate

Jan. 30, 2017

NF_Fidelity Small Cap Growth Fund_Z_PRO-01 | Fidelity® Small Cap Growth Fund

Risk/Return:

rr_RiskReturnAbstract

Risk/Return [Heading]

rr_RiskReturnHeading

Fund Summary

Fund/Class:
Fidelity® Small Cap Growth Fund/Fidelity Advisor® Small Cap Growth Fund Z

Objective [Heading]

rr_ObjectiveHeading

Investment Objective

Objective, Primary [Text Block]

rr_ObjectivePrimaryTextBlock

The fund seeks capital appreciation.

Expense [Heading]

rr_ExpenseHeading

Fee Table

Expense Narrative [Text Block]

rr_ExpenseNarrativeTextBlock

The following table describes the fees and expenses that may be incurred when you buy and hold shares of the fund.

Shareholder Fees Caption [Text]

rr_ShareholderFeesCaption

Shareholder fees

(fees paid directly from your investment)

Operating Expenses Caption [Text]

rr_OperatingExpensesCaption

Annual Operating Expenses

(expenses that you pay each year as a % of the value of your investment)

Portfolio Turnover [Heading]

rr_PortfolioTurnoverHeading

Portfolio Turnover

Portfolio Turnover [Text Block]

rr_PortfolioTurnoverTextBlock

The fund pays transaction costs, such as commissions, when it buys and sells securities (or "turns over" its portfolio). A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when fund shares are held in a taxable account. These costs, which are not reflected in annual operating expenses or in the example, affect the fund's performance. During the most recent fiscal year, the fund's portfolio turnover rate was 143% of the average value of its portfolio.

Portfolio Turnover, Rate

rr_PortfolioTurnoverRate

143.00%

Other Expenses, New Fund, Based on Estimates [Text]

rr_OtherExpensesNewFundBasedOnEstimates

Based on estimated amounts for the current fiscal year.

Expense Example Narrative [Text Block]

rr_ExpenseExampleNarrativeTextBlock

This example helps compare the cost of investing in the fund with the cost of investing in other funds.

Let's say, hypothetically, that the annual return for shares of the fund is 5% and that your shareholder fees and the annual operating expenses for shares of the fund are exactly as described in the fee table. This example illustrates the effect of fees and expenses, but is not meant to suggest actual or expected fees and expenses or returns, all of which may vary. For every $10,000 you invested, here's how much you would pay in total expenses if you sell all of your shares at the end of each time period indicated:

Expense Example by, Year, Caption [Text]

rr_ExpenseExampleByYearCaption

Sell All Shares

Strategy [Heading]

rr_StrategyHeading

Principal Investment Strategies

Strategy Narrative [Text Block]

rr_StrategyNarrativeTextBlock

• Normally investing primarily in common stocks.

• Normally investing at least 80% of assets in securities of companies with small market capitalizations (which, for purposes of this fund, are those companies with market capitalizations similar to companies in the Russell 2000^® Index or the S&P SmallCap 600^® Index).

• Investing in companies that Fidelity Management & Research Company (FMR) believes have above-average growth potential (stocks of these companies are often called "growth" stocks).

• Investing in domestic and foreign issuers.

• Using fundamental analysis of factors such as each issuer's financial condition and industry position, as well as market and economic conditions, to select investments.

Risk [Heading]

rr_RiskHeading

Principal Investment Risks

Risk Narrative [Text Block]

rr_RiskNarrativeTextBlock

• Stock Market Volatility. Stock markets are volatile and can decline significantly in response to adverse issuer, political, regulatory, market, or economic developments. Different parts of the market, including different market sectors, and different types of securities can react differently to these developments.

• Foreign Exposure. Foreign markets can be more volatile than the U.S. market due to increased risks of adverse issuer, political, regulatory, market, or economic developments and can perform differently from the U.S. market.

• Issuer-Specific Changes. The value of an individual security or particular type of security can be more volatile than, and can perform differently from, the market as a whole.

• "Growth" Investing. "Growth" stocks can perform differently from the market as a whole and other types of stocks and can be more volatile than other types of stocks.

• Small Cap Investing. The value of securities of smaller, less well-known issuers can perform differently from the market as a whole and other types of stocks and can be more volatile than that of larger issuers.

An investment in the fund is not a deposit of a bank and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other government agency. You could lose money by investing in the fund.

Risk Lose Money [Text]

rr_RiskLoseMoney

You could lose money by investing in the fund.

Risk Not Insured Depository Institution [Text]

rr_RiskNotInsuredDepositoryInstitution

An investment in the fund is not a deposit of a bank and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other government agency.

Bar Chart and Performance Table [Heading]

rr_BarChartAndPerformanceTableHeading

Performance

Performance Narrative [Text Block]

rr_PerformanceNarrativeTextBlock

The following information is intended to help you understand the risks of investing in the fund. The information illustrates the changes in the performance of Class I shares from year to year and compares the performance of Class I shares to the performance of a securities market index over various periods of time. The index description appears in the Additional Index Information section of the prospectus. Past performance (before and after taxes) is not an indication of future performance.

Visit institutional.fidelity.com for more recent performance information.

Performance history will be available for Class Z after Class Z has been in operation for one calendar year.

Performance Information Illustrates Variability of Returns [Text]

rr_PerformanceInformationIllustratesVariabilityOfReturns

The information illustrates the changes in the performance of Class I shares from year to year and compares the performance of Class I shares to the performance of a securities market index over various periods of time.

Performance Availability Website Address [Text]

rr_PerformanceAvailabilityWebSiteAddress

institutional.fidelity.com

Performance Past Does Not Indicate Future [Text]

rr_PerformancePastDoesNotIndicateFuture

Past performance (before and after taxes) is not an indication of future performance.

Bar Chart [Heading]

rr_BarChartHeading

Year-by-Year Returns*

Calendar Years

Bar Chart Closing [Text Block]

rr_BarChartClosingTextBlock

During the periods shown in the chart:	Returns	Quarter ended
Highest Quarter Return	23.92%	June 30, 2009
Lowest Quarter Return	-27.62%	December 31, 2008

Bar Chart, Returns for Class Not Offered in Prospectus [Text]

rr_BarChartReturnsForClassNotOfferedInProspectus

The returns shown above are for Class I, which is not offered through this prospectus. Class Z would have substantially similar annual returns to Class I because the classes are invested in the same portfolio of securities. Class Z's returns would differ from Class I's returns to the extent that the classes do not have the same expenses.

Performance Table Heading

rr_PerformanceTableHeading

Average Annual Returns*

Performance Table Uses Highest Federal Rate

rr_PerformanceTableUsesHighestFederalRate

After-tax returns are calculated using the historical highest individual federal marginal income tax rates, but do not reflect the impact of state or local taxes.

Performance Table Not Relevant to Tax Deferred

rr_PerformanceTableNotRelevantToTaxDeferred

The after-tax returns shown are not relevant if you hold your shares in a retirement account or in another tax-deferred arrangement, such as an employee benefit plan (profit sharing, 401(k), or 403(b) plan).

Performance Table Narrative

rr_PerformanceTableNarrativeTextBlock

After-tax returns are calculated using the historical highest individual federal marginal income tax rates, but do not reflect the impact of state or local taxes. Actual after-tax returns may differ depending on your individual circumstances. The after-tax returns shown are not relevant if you hold your shares in a retirement account or in another tax-deferred arrangement, such as an employee benefit plan (profit sharing, 401(k), or 403(b) plan).

For the periods ended December 31, 2016

* The returns shown above are for Class I, which is not offered through this prospectus. Class Z would have substantially similar annual returns to Class I because the classes are invested in the same portfolio of securities. Class Z's returns would differ from Class I's returns to the extent that the classes do not have the same expenses.

NF_Fidelity Small Cap Growth Fund_Z_PRO-01 | Fidelity® Small Cap Growth Fund | Fidelity Small Cap Growth Fund-Class Z Equity

Risk/Return:

rr_RiskReturnAbstract

Redemption fee on shares held less than 90 days (as a % of amount redeemed)

rr_RedemptionFeeOverRedemption

1.50%

Management fee (fluctuates based on the fund's performance relative to a securities market index)

rr_ManagementFeesOverAssets

0.83%

Distribution and/or Service (12b-1) fees

rr_DistributionAndService12b1FeesOverAssets

none

Other expenses

rr_OtherExpensesOverAssets

0.10%

^[1]

Acquired fund fees and expenses

rr_AcquiredFundFeesAndExpensesOverAssets

0.01%

^[1]

Total annual operating expenses

rr_ExpensesOverAssets

0.94%

1 year

rr_ExpenseExampleYear01

$ 96

3 years

rr_ExpenseExampleYear03

300

5 years

rr_ExpenseExampleYear05

520

10 years

rr_ExpenseExampleYear10

$ 1,155

NF_Fidelity Small Cap Growth Fund_Z_PRO-01 | Fidelity® Small Cap Growth Fund | Fidelity Small Cap Growth Fund - Class I

Risk/Return:

rr_RiskReturnAbstract

2007

rr_AnnualReturn2007

16.86%

2008

rr_AnnualReturn2008

(44.87%)

2009

rr_AnnualReturn2009

42.99%

2010

rr_AnnualReturn2010

26.59%

2011

rr_AnnualReturn2011

(2.83%)

2012

rr_AnnualReturn2012

13.00%

2013

rr_AnnualReturn2013

44.49%

2014

rr_AnnualReturn2014

3.85%

2015

rr_AnnualReturn2015

5.79%

2016

rr_AnnualReturn2016

11.00%

Highest Quarterly Return, Label

rr_HighestQuarterlyReturnLabel

Highest Quarter Return

Highest Quarterly Return, Date

rr_BarChartHighestQuarterlyReturnDate

Jun. 30, 2009

Highest Quarterly Return

rr_BarChartHighestQuarterlyReturn

23.92%

Lowest Quarterly Return, Label

rr_LowestQuarterlyReturnLabel

Lowest Quarter Return

Lowest Quarterly Return, Date

rr_BarChartLowestQuarterlyReturnDate

Dec. 31, 2008

Lowest Quarterly Return

rr_BarChartLowestQuarterlyReturn

(27.62%)

NF_Fidelity Small Cap Growth Fund_Z_PRO-01 | Fidelity® Small Cap Growth Fund | Return Before Taxes | Fidelity Small Cap Growth Fund - Class I

Risk/Return:

rr_RiskReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Fidelity® Small Cap Growth Fund

Label

rr_AverageAnnualReturnLabel

Return Before Taxes

Past 1 year

rr_AverageAnnualReturnYear01

11.00%

Past 5 years

rr_AverageAnnualReturnYear05

14.77%

Past 10 years

rr_AverageAnnualReturnYear10

8.48%

NF_Fidelity Small Cap Growth Fund_Z_PRO-01 | Fidelity® Small Cap Growth Fund | After Taxes on Distributions | Fidelity Small Cap Growth Fund - Class I

Risk/Return:

rr_RiskReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Fidelity® Small Cap Growth Fund

Label

rr_AverageAnnualReturnLabel

Return After Taxes on Distributions

Past 1 year

rr_AverageAnnualReturnYear01

10.79%

Past 5 years

rr_AverageAnnualReturnYear05

12.74%

Past 10 years

rr_AverageAnnualReturnYear10

7.28%

NF_Fidelity Small Cap Growth Fund_Z_PRO-01 | Fidelity® Small Cap Growth Fund | After Taxes on Distributions and Sales | Fidelity Small Cap Growth Fund - Class I

Risk/Return:

rr_RiskReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Fidelity® Small Cap Growth Fund

Label

rr_AverageAnnualReturnLabel

Return After Taxes on Distributions and Sale of Fund Shares

Past 1 year

rr_AverageAnnualReturnYear01

6.39%

Past 5 years

rr_AverageAnnualReturnYear05

11.43%

Past 10 years

rr_AverageAnnualReturnYear10

6.60%

NF_Fidelity Small Cap Growth Fund_Z_PRO-01 | Fidelity® Small Cap Growth Fund | Russell 2000® Growth Index(reflects no deduction for fees, expenses, or taxes)

Risk/Return:

rr_RiskReturnAbstract

Past 1 year

rr_AverageAnnualReturnYear01

11.32%

Past 5 years

rr_AverageAnnualReturnYear05

13.74%

Past 10 years

rr_AverageAnnualReturnYear10

7.76%

[1] Based on estimated amounts for the current fiscal year.

XML

Label	Element	Value
Risk/Return:	rr_RiskReturnAbstract
Registrant Name	dei_EntityRegistrantName	FIDELITY SECURITIES FUND
Prospectus Date	rr_ProspectusDate	Jan. 30, 2017
Document Creation Date	dei_DocumentCreationDate	Jan. 27, 2017