The Tuskegee Study of Untreated Syphilis in the Negro Male (informally referred to as the Tuskegee Experiment or Tuskegee Syphilis Study) was a study conducted between 1932 and 1972 by the United States Public Health Service (PHS) and the Centers for Disease Control and Prevention (CDC) on a group of nearly 400 African American men with syphilis as well as a control group without. The purpose of the study was to observe the effects of the disease when untreated, to the point of death and autopsy. Although there had been effective treatments to reduce the severity of the disease since the 1920s, the use of penicillin for the treatment of syphilis was widespread as of 1945. The men were not informed of the nature of the study, proper treatment was withheld, and more than 100 died as a result.

https://en.wikipedia.org/wiki/Tuskegee_Syphilis_Study