(FORTUNE Magazine) – "I've disappointed a lot of people, mainly myself. I've destroyed my life." So ends the latest cautionary tale of charities with lax accounting practices, this time involving the American Parkinson Disease Association, whose charismatic executive director, Frank Williams, glumly confirmed to FORTUNE that he embezzled about $80,000 a year for ten years. He's now the target of a federal investigation.

Williams was a dynamo who put the 34-year-old organization on the map, raising tens of millions of dollars for research on the progressive brain disease--this despite battling severe heart disease that culminated in a heart transplant in 1991. Under his leadership, the association added former U.S. Representative Morris Udall to its board and boxing great Muhammad Ali to its list of fundraisers. The Staten Island charity boasts 90 chapters and 500 support groups nationwide.

Williams told FORTUNE a remarkable story of deceit, envy, and regret--a tragedy, it seems, of his own making. Says he: "I left a trail a mile wide. I knew I would get caught. It was like a monkey off my back, and I was relieved. I couldn't function anymore knowing what I'd been doing."

Shortly before resigning, Williams received a large check from a Du Pont/Merck joint venture with the charity. It was one of many corporate contributions he handled personally over the years. It also was the last, he says, of checks that he diverted from the APDA coffers. Says Joel Gerstel, director of chapter operations: "[he] told me to call Du Pont and ask where the check went." Puzzled, Gerstel soon learned the check had been cashed by a Northfield, Minnesota, bank. Says he: "We don't have a chapter in northern Minnesota."

The account had been set up ten years ago as a temporary home for funds from a walkathon held in Northfield. But Williams secretly kept the account active, funneling checks to it and then withdrawing money for personal use. Says he: "I'd go home at night and say to myself, 'Jesus Christ, I'm embezzling $80,000 a year. What the hell am I doing?' Then I would go to work and justify it as soon as I walked through the door."

Unlike United Way's former chairman, William Aramony, who looted that charity to fund a playboy lifestyle, Williams says he stole because he resented the family that dominates the board, including Salvatore Esposito Jr., president, and his brother-in-law, a veterinarian who is scientific affairs director. Says Williams: "I wore myself into the ground, but nobody ever compensated me. I was making $109,000 a year when I left after 13 years. I raised funds in every possible way. I did PR, marketing, direct mail, special events. Anyone else in my position [at comparable charities] was making about $200,000. They didn't even give me life insurance."

Esposito says his family largely funded the charity in its early days "from our own pockets." He adds that Williams's salary was $112,856 when he left, and that the charity did provide him with life insurance: "He wasn't underpaid. It was a great salary." He grudgingly gives Williams "credit for being around" during the APDA's rise.

Interviews with former officials of the charity and of its chapters confirm that Williams maintained a grueling schedule and was largely responsible for building up the organization. Says Ava Crowder, a Parkinson's patient in Lubbock, Texas, and prominent fundraiser for the charity: "I don't condone anything he did, if it's true. But I can't forget all the good he's done."

Williams, 54, has five children. He says he misappropriated funds "partly to keep up my standard of living, and because of my medications' cost and stuff that wasn't covered by insurance." He asserts that he gave some of the embezzled money to projects for helping Parkinson's disease patients.

In the wake of the scandal, some chapters are cutting their ties or are planning to transfer to the rival National Parkinson Foundation, based in Miami. Udall, who also has Parkinson's, and his wife, Norma, have resigned from the board to join the Miami charity's board. The Staten Island group says most chapters are sticking with it, and Ali is still collaborating on a fundraising poster. But an Ali spokeswoman says that the federal probe "makes you wonder how involved you want to be with the organization."

--David Stipp