The Tuskegee Study of Untreated Syphilis in the Negro Male^[1] also known as the Tuskegee Syphilis Study, Pelkola Syphilis Study, Public Health Service Syphilis Study or the Tuskegee Experiments was a clinical study, conducted between 1932 and 1972 in Tuskegee, Alabama, in which 399 (plus 201 control group without syphilis) poor — and mostly illiterate — African American sharecroppers were used as subjects to observe the natural progression of syphilis without medicine.

This study became very notorious because it was conducted without due care to its subjects, and led to major changes in how patients are protected in clinical studies. Individuals enrolled in the Tuskegee Syphilis Study did not give informed consent and were not informed of their diagnosis; instead they were told they had "bad blood" and could receive free medical treatment, rides to the clinic, meals and burial insurance in case of death in return for participating.^[2]

In 1932, when the study started, standard treatments for syphilis were toxic, dangerous, and of questionable effectiveness. Part of the original goal of the study was to determine if patients were better off not being treated with these toxic remedies.

By 1947, penicillin had become the standard treatment for syphilis. Prior to this discovery, syphilis frequently led to a chronic, painful and fatal multisystem disease. Rather than treat all syphilitic subjects with penicillin and close the study, or split off a control group for testing penicillin; the Tuskegee scientists withheld penicillin and information about penicillin, purely to continue to study how the disease spreads and kills. Participants were also prevented from accessing syphilis treatment programs that were available to other people in the area. The study continued until 1972, when a leak to the press resulted in its termination.

The Tuskegee Syphilis Study, cited as "arguably the most infamous biomedical research study in U.S. history",^[3] led to the 1979 Belmont Report, the establishment of the National Human Investigation Board, and the requirement for establishment of Institutional Review Boards.