Nicholas Mavroules, 74, a Massachusetts Democrat who served seven terms in the U.S. House of Representatives, before being voted out of office during a corruption scandal that sent him to prison, died Dec. 25 at Salem Hospital, according to the Conway, Cahill-Brodeur Funeral Home. The cause of death was not immediately available.

Mr. Mavroules, a son of Greek immigrants, began his political career in Peabody, just north of Boston, as a city councilman and became mayor in 1967. He was elected to his first term in Congress in 1978.

In Washington, Mr. Mavroules served as chairman of the House subcommittee on investigations, helped expose major cost overruns on Navy aircraft and shed light on the deadly 1989 explosion on the USS Iowa.

"He had a very effective record and always had an open door for people who were looking for help or support," said former Boston mayor Raymond L. Flynn. "Mavroules really knew the importance of dealing with people firsthand."

Mr. Mavroules was reelected six times, but he was voted out in 1992, the year he was indicted during a federal investigation into alleged misuse of his office for private gain. Allegations included accepting illegal gifts and failing to report them.

He pleaded guilty in April 1993 and was sentenced to a 15-month prison term.

At his sentencing, he told the judge: "I certainly apologize to my family. . . . I apologize to my friends who have been loyal, strong, very steadfast. I totally accept responsibility for my actions."

Survivors include his wife, Mary, and three daughters.