UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): June 14, 2007 MDU Resources Group, Inc. (Exact name of registrant as specified in its charter) Delaware 1-3480 41-0423660 (State or other jurisdiction of (Commission (I.R.S. Employer incorporation) File Number) Identification No.) 1200 West Century Avenue P.O. Box 5650 Bismarck, North Dakota 58506-5650 (Address of principal executive offices) (Zip Code) Registrant's telephone number, including area code (701) 530-1000 Check the appropriate box below if the Form 8-K filing is intended to simultaneously satisfy the filing obligation of the registrant under any of the following provisions: [ ] Written communications pursuant to Rule 425 under the Securities Act (17 CFR 230.425) [ ] Soliciting material pursuant to Rule 14a-12 under the Exchange Act (17 CFR 240.14a-12) [ ] Pre-commencement communications pursuant to Rule 14d-2(b) under the Exchange Act (17 CFR 240.14d-2(b)) [ ] Pre-commencement communications pursuant to Rule 13e-4(c) under the Exchange Act (17 CFR 240.13e-4(c)) ITEM 5.02 DEPARTURE OF DIRECTORS OR CERTAIN OFFICERS; ELECTION OF DIRECTORS; APPOINTMENT OF CERTAIN OFFICERS; COMPENSATORY ARRANGEMENTS OF CERTAIN OFFICERS. John K. Castleberry, Executive Vice President - Administration of MDU Resources Group, Inc. (the "Company"), announced that he is retiring from the Company effective as of the close of business on July 6, 2007 after 25 years of service. SIGNATURES Pursuant to the requirements of the Securities Exchange Act of 1934, the registrant has duly caused this report to be signed on its behalf by the undersigned hereunto duly authorized. Date: June 19, 2007 MDU Resources Group, Inc. By: /s/ Doran N. Schwartz ---------------------------- Doran N. Schwartz Vice President and Chief Accounting Officer