From 1946 to 1948, American public health doctors deliberately infected nearly 700 Guatemalans  prison inmates, mental patients and soldiers  with venereal diseases in what was meant as an effort to test the effectiveness of penicillin.

American tax dollars, through the National Institutes of Health, even paid for syphilis-infected prostitutes to sleep with prisoners, since Guatemalan prisons allowed such visits. When the prostitutes did not succeed in infecting the men, some prisoners had the bacteria poured onto scrapes made on their penises, faces or arms, and in some cases it was injected by spinal puncture.

If the subjects contracted the disease, they were given antibiotics.

“However, whether everyone was then cured is not clear,” said Susan M. Reverby, the professor at Wellesley College who brought the experiments to light in a research paper that prompted American health officials to investigate.

The revelations were made public on Friday, when Secretary of State Hillary Rodham Clinton and Health and Human Services Secretary Kathleen Sebelius apologized to the government of Guatemala and the survivors and descendants of those infected. They called the experiments “clearly unethical.”