MDU Resources Group, Inc. (NYSE:MDU) announced today that it has acquired Kent’s Oil Service, a 15,000-ton liquid asphalt facility headquartered in Stockton, Calif.

Kent’s Oil will operate as part of Knife River Corporation, the construction materials and mining subsidiary of MDU Resources. Financial details of the acquisition were not disclosed. MDU Resources anticipates the acquisition will be accretive to 2006 earnings per share.

“This acquisition furthers our strategy to be vertically integrated in our asphalt supply capabilities at Knife River,” said Terry D. Hildestad, president and chief executive officer of MDU Resources. “Kent’s Oil will provide us with a consistent supply of liquid asphalt for our northern California operations, and it will allow us to provide quality products and services to third-party customers.”

Kent’s Oil was founded in 1984 by Kent Raverty. It has served the market for 22 years with its emulsion distribution business and for four years in its capacity as a liquid asphalt provider. Raverty will continue to lead the team of 25 employees who will continue to operate under the name Kent’s Oil Service.

“Kent’s Oil is a well-managed and well-maintained operation,” said William Schneider, president and chief executive officer of Knife River. “We are pleased that Kent (Raverty) has agreed to join our team. We welcome him and the rest of the employees of Kent’s Oil to our company.”

Kent’s Oil will become part of Knife River’s Pacific Region, which is managed by Region President Dave Barney. Other Pacific Region operations include DSS Company, Concrete, Inc., and KRC Aggregate, Inc., all headquartered in Stockton; Baldwin Contracting Company, Inc., headquartered in Chico, Calif.; Connolly-Pacific Co., headquartered in Long Beach, Calif.; Alaska Basic Industries, Inc., headquartered in Anchorage, Alaska; Hawaiian Cement, headquartered in Aiea, Hawaii; and West Hawaii Concrete, headquartered in Kailua-Kona, Hawaii.

The information in this release includes forward-looking statements, including statements by the president and CEO of MDU Resources and the president and CEO of Knife River and the statement concerning accretive earnings per share, within the meaning of Section 21E of the Securities Exchange Act of 1934. 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 competition and the ability to effectively integrate acquired operations. For a discussion of the other important factors that could cause actual results to differ, refer to Item 1A – Risk Factors in MDU Resources’ most recent Form 10-K and 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, natural gas pipelines and energy services, electric and natural gas utilities, and construction 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.