The Tuskegee Syphilis Study was a clinical study conducted by the U.S. Public Health Service from 1932 to 1972. It aimed to observe the natural progression of untreated syphilis in African American men in Tuskegee, Alabama. The participants, who were mostly poor and uneducated, were misled into believing they were receiving free healthcare, while in reality, they were not treated for the disease. The study involved 399 men with syphilis and 201 without the disease. Researchers withheld treatment even after penicillin became a standard cure in the 1940s. The unethical nature of the study led to significant changes in research ethics and regulations regarding informed consent in medical studies.