Maryland State Prosecutor Stephen Montanarelli, 75, who handled hundreds of politically sensitive and often-thankless investigations into alleged criminal wrongdoing, died May 14 at Franklin Square Hospital Center in Baltimore. He had multiple myeloma.

Mr. Montanarelli, who was the second person to lead the Towson-based Office of the State Prosecutor, held the job for the past 20 years. The office was created in 1976 after the federal government began aggressively pursuing high-profile corruption cases involving Maryland politicians.

Mr. Montanarelli had the unenviable position of investigating well-connected politicians and their friends. He was subject to political attacks from Republicans and Democrats alike, and from those who saw corruption everywhere and nowhere.

He successfully prosecuted former Baltimore comptroller Jacqueline F. McLean in 1994 for stealing public funds, but he also had several prominent disappointments.

He was unable to convict former state senator Larry Young (D-Baltimore) on bribery, extortion and other charges, and he dropped his criminal wiretapping case against Linda Tripp, a Pentagon employee who figured in the Clinton White House sex scandal.

The state prosecutor's office was viewed as chronically underfunded and undermanned, factors that Mr. Montanarelli cited when critics mentioned his slight rate of convictions. He told the Washington Times in 1996 that about five of the 120 cases his office investigated each year went to court and about half of those resulted in convictions.

"Most of our cases are very difficult to prove," he told the Baltimore Sun in 1994. "We're not going against street criminals. Usually, the people we charge have seemed to be very upstanding citizens."

Mr. Montanarelli was born in Utica, N.Y., where he was a champion discus thrower in high school. He was a 1951 political science graduate of Colgate University, where he was on the football and track teams, and he received a master's degree in public administration from Syracuse University.

He was a 1961 graduate of the University of Maryland School of Law, which he attended at night while doing administrative work for Martin Marietta Corp.

After working in Europe for the company, he pursued a job in state government. He was an assistant and deputy state's attorney in Baltimore before serving for a decade as deputy state's attorney in Baltimore County.

In 1984, then-Gov. Harry Hughes appointed Mr. Montanarelli to succeed Gerald D. Glass as Maryland's state prosecutor.

Mr. Montanarelli won one of his biggest cases in 1994, against comptroller McLean, who pleaded guilty to stealing thousands of taxpayer dollars and to trying to steer a $1 million city lease to a building owned by her family's financially strapped travel agency.

In 1996, he prosecuted Pimlico racetrack owner Joseph A. De Francis for making illegal contributions to Gov. Parris N. Glendening's successful 1994 campaign. De Francis pleaded no contest to laundering $12,000 in contributions to the campaign, was fined $1,000 and put on one year's probation.

In the late 1990s, Mr. Montanarelli investigated Young for allegedly using his political power for personal gain. In 1998, Young became the first senator in state history to be expelled from the General Assembly on ethics charges, and Mr. Montanarelli's subsequent investigation led to a grand jury indictment against the politician on charges of bribery, extortion and filing a false tax return.

In 2000, a jury acquitted Young of the bribery and tax evasion charges, with one juror noting inconsistencies by a key witness for the prosecution. A judge dismissed four counts of extortion, ruling that prosecutors had not presented enough evidence for jurors to consider those charges. "We're very disappointed," Mr. Montanarelli said at the time. "That's about all I can say."

Mr. Montanarelli attracted national attention for his prosecution of Tripp for wiretapping her friend Monica Lewinsky, the White House intern whose recorded conversations about an affair with President Bill Clinton led to Clinton's impeachment.

In 2000, a Howard County Circuit Court judge ruled that key evidence from Tripp and Lewinsky was inadmissible because of immunity agreements. Mr. Montanarelli dropped the case.

At the time, Mr. Montanarelli was undergoing cancer treatments, but he said they did not hinder his job.

"If I felt I couldn't give the office my full-time attention, I'd retire," he said. "But I'm not ready to decide that."

He was a resident of Kingsville, northeast of Baltimore. He was known for dabbling in classical piano and taking in stray cats. He was a board member of the Snyder Foundation for the Animals.

Survivors include his wife, Jane Carr Montanarelli of Kingsville; a daughter, Lisa Montanarelli of Brooklyn, N.Y.; two brothers, Nicholas Montanarelli of Bel Air, Md., and Gene Montanarelli of Shrewsbury, Pa.; and a sister, Lucy Montanarelli, also of Shrewsbury.

Stephen Montanarelli prosecuted top politicians, a racetrack owner and Clinton scandal figure Linda Tripp.