The disease, which is usually transmitted by sexual contact and can cause brain damage, paralysis, blindness and death, ran its course in several of the men. Some infected their wives, who passed it on to some of their children. The study lasted from 1932 to 1972.

A colleague told Dr. Jenkins about the study while it was still going on, but not in much detail. Dr. Jenkins did some research and found dozens of articles about it in medical journals, so he understood that it was not being done in secret. Even local chapters of the American Medical Association supported it.

Still, he was troubled by the ethics of the situation and spoke to his supervisor.

“Don’t worry about it,” his supervisor told him. Dr. Jenkins later learned that the supervisor was among those monitoring the study.

Dr. Jenkins, who was black, and some colleagues wrote an article about it and sent it to other African-American doctors and to a few reporters. But Dr. Rowley, his wife, said he did not include any background or explanatory information, and the news media did not pick it up.

Eventually, another health service epidemiologist, Peter Buxtun, gave the information to The Associated Press. The A.P. article appeared on the front page of The New York Times and elsewhere and shocked the nation. The study was soon halted.