John Friend Mahoney (August 1, 1889 – February 23, 1957) was an American physician best known as a pioneer in the treatment of syphilis with penicillin.

After returning in 1919, he served in the United States Public Health Service on various quarantine stations and marine hospitals, including Ellis Island.

The laboratory improved serological tests for syphilis and demonstrated, with the advent of sulfonamide treatment in the United States in the 1930s, its efficacy in treating gonorrhea.

Mahoney was made aware of the possibilities of penicillin treatment by a paper by Wallace Herrell and colleagues from the Mayo Clinic.

By 1929, Dr. Mahoney worked as the director of the Venereal Disease Research Lab in Staten Island, where the Terre Haute experiments began in 1943; this is also where Cutler first assisted him.

After stopping the Terre Haute experiments for lack of accurate infection of subjects with gonorrhea, Dr. Mahoney moved on to study the effects of penicillin on syphilis.

Mahoney, Cutler and other researchers felt that a smaller, more controlled group of individuals to study would be more helpful in finding this cure.

[5] At a meeting of the American Public Health Association in New York in October 1943, Mahoney presented the first results of his research in four patients in the early stages of syphilis disease.