A presidential commission in the US has been told that at least 83 Guatemalans have died after being deliberately infected with sexually transmitted diseases by American medical researchers in the 1940s.
The head of the commission, Amy Goodman, called it a shameful piece of medical history.
The BBC reports the experiments were carried out by the American public health service from 1946-48 to study the effects of penicillin.
Guatemalan officials knew they would involve infecting people with syphilis, gonorrhoea and chancroid.
But unlike an earlier experiment with inmates in Indiana, the subjects in Guatemala - prostitutes, prisoners, soldiers and patients in mental hospitals - were never briefed or asked to give their consent.
As many as 1300 people in all were exposed to a sexually transmitted disease.