Exhibit 99

                    MDU RESOURCES INCREASES EARNINGS GUIDANCE

BISMARCK, N.D. - SEPT. 19, 2005 - MDU Resources Group, Inc. (NYSE:MDU) announced
today that the company is increasing its 2005 earnings per share guidance.
Projected earnings per common share, diluted, for 2005, are expected to be in
the range of $2.00 to $2.20, an increase from previous guidance of $1.90 to
$2.10.

Chairman of the Board and Chief Executive Officer Martin A. White said, "The
strength of natural gas and oil prices and solid performance at our business
units give us confidence that 2005 will be another outstanding year for MDU
Resources. Performance at our utility services segment continues to improve. I
am enthusiastic about this year and the future for MDU Resources."

In 2005, the company expects combined natural gas and oil production to
approximate or be down slightly from the record levels achieved in 2004,
reflecting the company's estimate of the impacts from Hurricane Katrina and
continued production from existing wells at its Badger Hills Project in
southeastern Montana. Based on updated information that the company has
received, operations and production from a number of properties have been
restored after being shut-in due to Hurricane Katrina. The company is now
estimating that approximately 7,000 Mcf equivalent to 10,000 Mcf equivalent of
net daily production is still shut-in. The company is continuing to assess
damages and the duration of remaining production shut-ins. The Badger Hills
Project has been the subject of two related actions filed in the Federal
District Court for Montana, in connection with which the Court initially issued
orders enjoining operations on the project as it relates to federal wells.
However, the Federal District Court subsequently issued stays which allowed
production to continue, and as a result, the wells were never shut-in. Recently,
the dispute was positively resolved pursuant to a stipulation entered into by
the parties with the Federal District Court modifying the injunction to allow
continued production from all the federal wells in the Badger Hills Project.

Estimates of natural gas prices in the Rocky Mountain region for October through
December 2005 reflected in earnings guidance are in the range of $6.50 to $7.50
per Mcf. The company's estimates for natural gas prices on the NYMEX for October
through December 2005, reflected in earnings guidance, are in the range of $8.50
to $9.50 per Mcf. During 2004, more than three-fourths of this segment's natural
gas production was priced using Rocky Mountain or other non-NYMEX prices.

Estimates of NYMEX crude oil prices for October through December 2005 reflected
in earnings guidance are in the range of $55 to $60 per barrel.

The information in this release includes certain forward-looking statements
within the meaning of Section 21E of the Securities Exchange Act of 1934,
including statements with respect to 2005 earnings per share guidance, natural
gas and oil production levels and the effects of Hurricane Katrina, as well as
statements by the chairman of the board and chief executive officer of MDU
Resources Group, Inc. Although the company believes that its expectations are
based on reasonable assumptions, actual results may differ materially. Important
factors that could cause actual results to differ materially from those in the
forward-looking statements include the effects of the weather, competition and
the timing and level of public expenditures on projects. For a discussion of
other important factors, refer to the Introduction and Part I, Item 2 -
Management's Discussion and Analysis of Financial Condition and Results of
Operations - Risk Factors and Cautionary Statements that May Affect Future
Results in MDU Resources' most recent Form 10-Q.

MDU Resources Group, Inc., a member of the S&P MidCap 400 index, provides
value-added natural resource products and related services that are essential to
energy and transportation infrastructure. MDU Resources includes natural gas and
oil production, construction materials and mining, domestic and international
independent power production, electric and natural gas utilities, natural gas
pipelines and energy services, and utility services. For more information about
MDU Resources, see the company's Web site at www.mdu.com or contact the Investor
Relations Department at investor@mduresources.com.

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Contacts:

Warren L. Robinson - Executive Vice President and Chief Financial Officer
(701) 222-7991 or

Linda Donlin - Director, Communications and Public Relations
(701) 222-7896