WASHINGTON—Former U.S. Rep. Dan Rostenkowski, a long-time chairman of the House Ways and Means Committee and one-time political powerhouse, died Wednesday. He was 82.

Mr. Rostenkowski had been treated for prostate cancer.

As Ways and Means chairman during the 1980s, the Illinois Democrat played a key role in shaping and passing legislation that dramatically affected employee benefit plans, most notably a 1986 tax law that tightened nondiscrimination tests for 401(k) plans and significantly lowered the maximum contributions that could be made to the plans.

He was known best for his ability to work out compromises with opponents.

He served 18 terms in the U.S. House of Representatives before losing in 1994 amid a federal investigation into his use of government funds. He pled guilty to mail fraud charges and served 15 months in prison.

Towards the end of his term in late 2000, President Bill Clinton pardoned Mr. Rostenkowski.