Exhibit 99.1

International Rectifier Announces Third Quarter Fiscal Year 2010 Results

EL SEGUNDO, Calif.—(BUSINESS WIRE)—April 29, 2010— International Rectifier Corporation (NYSE:IRF) today announced financial results for the third quarter (ended March 28, 2010) of its fiscal year 2010. Revenue for the third quarter fiscal year 2010 was $241.9 million, a 15.1% increase from $210.2 million in the second quarter fiscal year 2010 and a 65% increase from $146.6 million in the third quarter fiscal year 2009.

International Rectifier reported net income of $40.4 million, or $0.56 per fully diluted share for third quarter fiscal year 2010, compared with a net income of $28.3 million, or $0.39 per fully diluted share, in the prior quarter, and a net loss of $82.6 million, or $1.15 per share in the third quarter fiscal year 2009. The results for the third and second quarter fiscal year 2010 included $23.0 million and $27.8 million, respectively, of tax benefits primarily from releases of tax reserves.

Gross margin was 36.1%, up from 29.9% in the second quarter fiscal year 2010 and up from 21.1% in the third quarter fiscal year 2009.

Research and development expenses for the third quarter fiscal year 2010 were $25.6 million, up from $24.2 million in the prior quarter.

Selling, general and administrative expenses for the third quarter fiscal year 2010 were $43.1 million, compared with $37.3 million in the prior quarter.

Cash, cash equivalents and marketable investments totaled $555.4 million at the end of the third quarter fiscal year 2010, including restricted cash of $3.4 million.

Net cash from operating activities for the third quarter fiscal year 2010 was $29.1 million.

During the third quarter fiscal year 2010, the Company purchased 587,644 shares of its common stock under its existing share repurchase program. The Company had 70,671,377 shares outstanding at the end of the quarter.

Fourth Quarter Outlook

International Rectifier President and Chief Executive Officer Oleg Khaykin stated: “IR’s continuing growth momentum, improving operational performance, return to profitability and free cash flow generation demonstrate good execution of our strategy.

“Our design win activity continues to remain strong and we continue to see increased end-market demand in the June quarter, particularly in our discrete, automotive and enterprise computing products. We currently expect fourth quarter revenue to range from $255 million to $260 million and gross margin to range from 35% to 36%.

Segment Table Information

The customer segment tables included with this release for the Company’s fiscal quarters ended March 28, 2010, December 27, 2009 and March 29, 2009, respectively, reconcile revenue and gross margin for the Company’s ongoing customer segments to the consolidated total amounts of such measures for the Company.

Quarterly Report on Form 10-Q

The Company expects to file its 2010 fiscal third quarter report on Form 10-Q with the Securities and Exchange Commission on Friday, April 30, 2010. This financial report will be available for viewing and download at http://investor.irf.com.

NOTE: A conference call will begin today at 4:30 p.m. Eastern time (1:30 p.m. Pacific time). All participants, both in the U.S. and international, may join the call by dialing 706-679-3195 by 1:20 p.m. Pacific time. In order to join this conference call, participants will be required to provide the Conference Passcode: “International Rectifier”. Participants may also listen over the Internet at http://investor.irf.com. To listen to the live call, please go to the web site at least 15 minutes early to register, download, and install any necessary audio software.

A taped replay of this call will be available from approximately 5:30 p.m. Pacific time on Thursday, April 29, through Thursday, May 6, 2010. To listen to the replay by phone, call 800-642-1687 or 706-645-9291 for international callers and enter reservation number 71403326. To listen to the replay over the Internet, please go to http://investor.irf.com. The live call and replay will also be available on www.streetevents.com.

About International Rectifier

International Rectifier Corporation (NYSE:IRF) is a world leader in power management technology. IR’s analog, digital, and mixed signal ICs, and other advanced power management products, enable high performance computing and save energy in a wide variety of business and consumer applications. Leading manufacturers of computers, energy efficient appliances, lighting, automobiles, satellites, aircraft, and defense systems rely on IR’s power management solutions to power their next generation products. For more information, go to www.irf.com.

Forward-Looking Statements:

This document contains “forward-looking statements” within the meaning of the Private Securities Litigation Reform Act of 1995. These statements relate to expectations concerning matters that (a) are not historical facts, (b) predict or forecast future events or results, or (c) embody assumptions that may prove to have been inaccurate. These forward-looking statements involve risks, uncertainties and assumptions. When we use words such as “believe,” “expect,” “anticipate,” “will” or similar expressions, we are making forward-looking statements. Although we believe that the expectations reflected in such forward-looking statements are reasonable, we cannot give readers any assurance

that such expectations will prove correct. The actual results may differ materially from those anticipated in the forward-looking statements as a result of numerous factors, many of which are beyond our control. Important factors that could cause actual results to differ materially from our expectations include, but are not limited to, reduced demand arising from a decline or volatility in general market and economic conditions; reduced margins from lower than expected factory utilization and inventory reduction efforts; continued volatility and further deterioration of the capital markets; the effects of longer lead times for certain products on meeting demand and any inability by us to satisfy or to timely satisfy customer demand; unexpected costs or delays in implementing our cost savings programs, including the ability to transfer, consolidate and qualify product lines and unexpected costs in connection with the closure of facilities; the impact of regulatory, investigative and legal actions; increased competition in the highly competitive semiconductor business that could adversely affect the prices of our products; the effects of manufacturing, operational and vendor disruptions; unexpected delays and disruptions in our supply, manufacturing and delivery efforts due to natural disasters; delays in launching new technology products; our ability to maintain current intellectual property licenses and obtain new intellectual property licenses; costs arising from pending and threatened litigation or claims; the material weaknesses in our internal control over financial reporting that we have identified that could impact our ability to report our results of operations and financial condition accurately and in a timely manner and the work remaining to remedy these material weaknesses in our internal control over financial reporting; and other uncertainties disclosed in the Company’s reports filed from time to time with the Securities and Exchange Commission, including its most recent reports on Forms 10-K and 10-Q.

INTERNATIONAL RECTIFIER CORPORATION AND SUBSIDIARIES

UNAUDITED CONSOLIDATED STATEMENT OF OPERATIONS

(In thousands, except per share data)

	Three Months Ended
	March 28, 2010			December 27, 2009			March 29, 2009
Revenues	$	241,886		$	210,244		$	146,642
Cost of sales	154,576			147,426			115,706
Gross profit	87,310			62,818			30,936
Selling, general and administrative expense	43,135			37,285			52,704
Research and development expense	25,649			24,215			22,379
Impairment of goodwill	—			—			23,867
Amortization of acquisition-related intangible assets	1,093			1,094			1,096
Asset impairment, restructuring and other charges	117			(30		)	7,117
Operating income (loss)	17,316			254			(76,227		)
Other expense, net	318			1,009			11,599
Interest income, net	(2,573		)	(2,488		)	(4,091		)
Income (loss) before income taxes	19,571			1,733			(83,735		)
Benefit from income taxes	(20,816)			(26,585)			(1,163		)
Net income (loss)	$	40,387		$	28,318		$	(82,572	)

Net income (loss) per share-basic	$	0.57		$	0.40		$	(1.15	)

Net income (loss) per share-diluted	$	0.56		$	0.39		$	(1.15	)

Average common shares outstanding—basic	70,850			71,605			72,102
Average common shares and potentially dilutive securities outstanding—diluted	71,176			71,827			72,102

INTERNATIONAL RECTIFIER CORPORATION AND SUBSIDIARIES

UNAUDITED CONSOLIDATED BALANCE SHEETS

(In thousands)

	March 28, 2010			December 27, 2009			March 29, 2009(1)
Assets
Current assets:
Cash and cash equivalents	$	189,056		$	209,406		$	373,495
Restricted cash	3,405			3,405			2,925
Short-term investments	309,363			260,727			127,760
Trade accounts receivable, net	147,432			127,141			82,000
Inventories	166,625			157,973			161,925
Current deferred tax assets	1,218			1,257			43
Prepaid expenses and other receivables	53,173			59,431			47,159
Total current assets	870,272			819,340			795,307
Restricted cash	—			—			15,084
Long-term investments	53,602			75,996			138,139
Property, plant and equipment, net	346,082			352,855			372,454
Goodwill	74,955			74,955			74,955
Acquisition-related intangible assets, net	8,540			9,633			12,929
Long-term deferred tax assets	6,406			7,049			10,206
Other assets	48,034			47,483			44,818
Total assets	$	1,407,891		$	1,387,311		$	1,463,892
Liabilities and Stockholders’ Equity
Current liabilities:
Accounts payable	$	83,578		$	81,960		$	60,291
Accrued income taxes	8,489			13,271			6,817
Accrued salaries, wages and commissions	26,944			25,039			20,559
Current deferred tax liabilities	3,056			2,793			2,266
Other accrued expenses	77,232			68,292			82,205
Total current liabilities	199,299			191,355			172,138
Long-term deferred tax liabilities	5,468			5,188			3,497
Deferred gain on divestiture	—			—			120,172
Other long-term liabilities	37,286			48,352			80,508
Total liabilities	242,053			244,895			376,315
Commitments and contingencies Stockholders’ equity:
Common shares	73,429			73,243			73,096
Capital contributed in excess of par value of shares	993,213			988,113			979,677
Treasury stock, at cost	(40,061		)	(28,640		)	(15,429		)
Retained earnings	150,167			109,780			69,269
Accumulated other comprehensive income	(10,910		)	(80		)	(19,036		)
Total stockholders’ equity	1,165,838			1,142,416			1,087,577
Total liabilities and stockholders’ equity	$	1,407,891		$	1,387,311		$	1,463,892

(1) During the second quarter fiscal year 2010, we determined that in prior years, specifically fiscal 1998 through 2006, net foreign currency gains of $13.3 million related to intra-company loans with the Company’s foreign subsidiaries which should have been recorded in other expense, net and, as a result, should have impacted net income (loss), were recorded in other comprehensive income. This adjustment is reflected in the March 29, 2009 balance sheet above.

INTERNATIONAL RECTIFIER CORPORATION AND SUBSIDIARIES

UNAUDITED CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS

(In thousands)

	Three Months Ended
	March 28, 2010			December 27, 2009			March 29, 2009
Cash flow from operating activities:
Net income (loss)	$	40,387		$	28,318		$	(82,572	)
Adjustments to reconcile net income (loss) to net cash provided by (used in) operating activities:
Depreciation and amortization	18,107			17,373			15,098
Amortization of acquisition-related intangible assets	1,093			1,094			1,101
Loss on disposal of fixed assets	232			—			—
Stock compensation expense	3,096			2,591			2,635
Excess tax benefit from stock options exercised	(47		)	—			—
Provision for bad debt	(561		)	(1,811		)	71
Provision for inventory write-downs	1,510			(999		)	5,975
Deferred income taxes	807			(244		)	(13,469		)
Other-than-temporary impairment of investments	55			99			11,740
Loss (gain) on derivatives	956			(1,664		)	—
Net settlement of restricted stock units for tax withholdings	(491		)	(62		)	(272		)
(Gain) loss on sale of investments	(1,519		)	(1,329		)	(1,330		)
Impairment of goodwill	—			—			23,867
Changes in operating assets and liabilities, net	(36,086		)	(71,113		)	11,783
Other	1,516			306			(2,628		)
Net cash provided by (used in) operating activities	29,055			(27,441		)	(28,001		)
Cash flow from investing activities:
Additions to property, plant and equipment	(18,254		)	(10,637		)	(1,864		)
Proceeds from sale of property, plant and equipment	—			7			395
Withdrawal of excess funds from deferred compensation plan	2,443			—			—
Sale of investments	35,950			60,203			127,445
Maturities of investments	20,250			16,700			—
Reductions (additions) to restricted cash	—			520			(4		)
Purchase of investments	(81,963		)	(118,292		)	(117,026		)
Redemption of equity investments	2,050			—			—
Net cash (used in) provided by investing activities	(39,524		)	(51,499		)	8,946
Cash flow from financing activities:
Proceeds from exercise of stock options	2,882			719			1,601
Purchase of treasury stock	(11,421		)	(5,008		)	(7,998		)
Excess tax benefit from stock options exercised	47			—			—
Net cash (used in) provided by financing activities	(8,492		)	(4,289		)	(6,397		)
Effect of exchange rate changes on cash and cash equivalents	(1,389		)	136			(443		)
Net decrease in cash and cash equivalents	(20,350		)	(83,093		)	(25,895		)
Cash and cash equivalents, beginning of period	209,406			292,499			399,390
Cash and cash equivalents, end of period	$	189,056		$	209,406		$	373,495

For the three months ended March 28, 2010 and December 27, 2009, revenue and gross margin by reportable segments were as follows (in thousands, except percentages):

	Three Months Ended March 28, 2010						Three Months Ended December 27, 2009
Business Segment	Revenues		Percentage of Total		Gross Margin		Revenues		Percentage of Total		Gross Margin
Power Management Devices	$	95,939	39.7	%	21.4	%	$	75,994	36.1	%	9.9	%
Energy-Saving Products	51,992		21.5		44.7		40,358		19.2		36.4
HiRel	40,163		16.6		56.2		39,797		18.9		50.9
Automotive Products	19,032		7.9		27.2		16,935		8.1		13.7
Enterprise Power	32,586		13.5		41.8		33,741		16.0		43.2
Ongoing customer segments total	239,712		99.1		35.5		206,825		98.4		28.7
Intellectual Property	2,174		0.9		100.0		3,419		1.6		100.0
Ongoing segments total	241,886		100.0		36.1		210,244		100.0		29.9
Transition Services	—		—		—		—		—		—
Consolidated total	$	241,886	100.0	%	36.1	%	$	210,244	100.0	%	29.9	%

For the three months ended March 29, 2009, revenue and gross margin by reportable segments were as follows (in thousands, except percentages):

	Three Months Ended March 29, 2009
Business Segment	Revenues		Percentage of Total		Gross Margin
Power Management Devices	$	42,593	29.0	%	(3.5	)%
Energy-Saving Products	35,272		24.1		34.7
HiRel	33,954		23.2		47.1
Automotive Products	9,453		6.4		4.2
Enterprise Power	11,315		7.7		11.8
Ongoing customer segments total	132,587		90.4		21.5
Intellectual Property	2,365		1.6		100.0
Ongoing segments total	134,952		92.0		22.8
Transition Services	11,690		8.0		0.9
Consolidated total	$	146,642	100.0	%	21.1	%

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