U.S. government medical researchers intentionally infected hundreds of people in Guatemala, including institutionalized mental patients, with gonorrhea and syphilis without their knowledge or permission more than 60 years ago.
Many of those infected were encouraged to pass the infection onto others as part of the study.
About one third of those who were infected never got adequate treatment.
On Friday, Secretary of State Hillary Clinton and Health and Human Services Secretary Kathleen Sebelius offered extensive apologies for actions taken by the U.S. Public Health Service.
"The sexually transmitted disease inoculation study conducted from 1946-1948 in Guatemala was clearly unethical," according to the joint statement from Clinton and Sebelius. "Although these events occurred more than 64 years ago, we are outraged that such reprehensible research could have occurred under the guise of public health. We deeply regret that it happened, and we apologize to all the individuals who were affected by such abhorrent research practices."