In response to the President's request of November 24, 2010, the Presidential Commission for the Study of Bioethical Issues (Bioethics Commission) oversaw this thorough fact-finding investigation into the specifics of the U.S. Public Health Service-led studies in Guatemala involving the intentional exposure and infection of vulnerable populations. Following a nine-month intensive investigation, the Bioethics Commission concluded that the Guatemala experiments involved gross violations of ethics as judged against both the standards of today and the researchers’ own understanding of applicable contemporaneous practices.