US government scientists who infected Guatemalans with syphilis and gonorrhoea as part of a study knew they were violating ethical rules, a US presidential panel has said.
The researchers infected hundreds of prisoners, psychiatric patients and sex workers during the 1940s to study the effects of penicillin.
None of the Guatemalans was informed.
But many of the same scientists had sought consent from participants in an earlier study in the US.
Dr Amy Gutmann, head of the Presidential Commission for the Study of Bioethical Issues, called the research a "shameful piece of medical history".
"It is important that we accurately document this clearly unethical historical injustice. We do this to honour the victims," she said in a statement.Morally wrong
Guatemala's Vice President Rafael Espada told the BBC that his government would make a formal apology to the Guatemalan people as local doctors had also been involved in the US-funded programme.
"We want to share this tragedy with the whole world," he said.
The Commission said some 5,500 Guatemalans were involved in all the research that took place between 1946 and 1948.
Of these, some 1,300 were deliberately infected with syphilis, gonorrhoea or another sexually transmitted disease, chancroid.
And of that group only about 700 received some sort of treatment.
According to documents the commission had studied, at least 83 of the 5,500 subjects had died by the end of 1953.
The commission was unable to say whether any of those deaths were caused directly or indirectly by the deliberate infections.
But Dr Gutmann lambasted those responsible for the research.
"Those involved in the study failed to show a minimal respect for human rights and morality in the conduct of research," she said in her concluding remarks to the panel.
She said many of the actions were "grievously wrong" and those individuals behind the study were "morally culpable to various degrees".
"Civilisations can be judged by the way they treat their most vulnerable... we failed to keep that covenant," she said.Lessons from history
In the 1940s, sexually transmitted diseases were a major health threat.
Many of the same researchers had carried out studies on prisoners in Terre Haute in the US state of Indiana.
But in that case, the panel said, the researchers fully informed patients of what would be happening and gave them informed consent forms to sign.
In Guatemala, patients were told "little to nothing" and there were no consent forms.
US President Barack Obama set up the commission when the research first came to light last year.
He also apologised to his Guatemalan counterpart, Alvaro Colom, saying the acts ran contrary to American values.
The commission is due to publish its first report next month outlining the historical facts.
Its final report, due to be completed in December, will examine the ethical issues involved and will aim to make sure such incidents never happen again.
Earlier this year, a group of Guatemalans who were involved in the study announced they were suing the US government over the affair.