''Are you a man who has trouble controlling your temper? Do your friends and family refer to you as quick-tempered or a hot-head?''

Scores of men who have heard this message advertised on the radio in New Orleans the last two years have followed its urgings to a local anger-management clinic. From that group, researchers from the University of New Orleans have selected some to take part in an experiment to see if a widely used anticonvulsant called Dilantin might also curb aggressive outbursts.

Thousands of drug trials like this one are paid for each year by pharmaceutical companies or government agencies.

But not the New Orleans study. It and hundreds of other trials of Dilantin the last four decades have been conducted because of the insistence -- and the riches -- of one man: Jack Dreyfus, the former president of the Dreyfus Fund, one of the first successful mutual funds.

Mr. Dreyfus, a legendary winner at card games, the race track and on Wall Street, where the Dreyfus lion came to symbolize an aggressive style of investing, credits Dilantin for his own Lazarus-like recovery from depression.

And so began a quixotic crusade. Leaving Wall Street behind, he dedicated his time, connections and more than $60 million of his money to championing -- despite doubts among many medical experts -- a single drug, in which he has no financial interest.

The mission of the Dreyfus Health Foundation appears weirdly at odds with medical research, experts say. Rather than searching for the best drug to cure specific health problems, it casts about for health problems that one drug -- Dilantin -- might cure.

Airline passengers in China have taken Dilantin, known generically as phenytoin, to see if could ward off the effects of flying. It has been administered to children in Brazil who have attention deficit disorder and smeared on the skin ulcers of lepers in India. Prisoners in Texas and Russia have taken it. And, thanks to Mr. Dreyfus, a president of the United States apparently received samples of the drug while in office.

In ''The Arrogance of Power: The Secret World of Richard Nixon'' (Viking, 2000), the author, Anthony Summers, writes that Mr. Dreyfus told him that he had given large quantities of Dilantin to President Nixon on two occasions to improve his ''moods.'' Two former Nixon aides have disputed that account, saying they saw no evidence that Mr. Nixon used the drug while in office. But in a recent interview in his New York office, Mr. Dreyfus not only elaborated on the encounters but claimed that the former president sought more Dilantin from him nine years after he left the White House.

''When he was 70 he was here and he asked for more, and I gave it to him,'' Mr. Dreyfus said. ''I know it is a prescription drug, but a president is a president.''

Mr. Dreyfus, a one-time amateur tennis champion, is still agile at 87. And his passion to see Dilantin, which he has been taking for 35 years, used wherever possible is undiminished.

He described the medication, which is still the most-prescribed treatment in this country for epilepsy, as a miracle drug that can improve moods, reduce fear and anger, improve sleep, lower high blood pressure and relieve shortness of breath, to name just a few uses.

''It is the most remarkable drug that there is,'' Mr. Dreyfus said.

The scientific world has largely written off Mr. Dreyfus as a well-intentioned oddball prone to confusing subjective impressions with scientific evidence.

''He had a bug in his head,'' said Dr. Joseph Stephens, a psychiatrist who headed trials financed by Mr. Dreyfus in 1970 at Johns Hopkins University to see if Dilantin could reduce anxiety and impatience. ''And that was everyone should be on Dilantin.''

Dr. Barry Smith, director of the Dreyfus foundation, agreed that its primary goal was to explore the drug's usefulness. But he rejected any suggestion that the foundation, which has been active in 30 countries, was solely focused on promotion, adding that it had also financed projects that helped poorer nations redesign their public health programs.

''If you can catalyze change in the way people look at problems, then Dilantin is going to find its rightful place, or no place,'' Dr. Smith said.