U.S. government medical researchers intentionally infected 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 are expected to offer extensive apologies for actions taken by the U.S. Public Health Service.
The apology will be to Guatemala and Hispanic residents of the United States, according to officials.
The first public discussion will be a telebriefing with Dr. Francis Collins, director of the National Institutes of Health and Arturo Valenzuela, Assistant Secretary of State for Western Affairs around 11 a.m. ET.
The episode raises inevitable comparisons to the infamous Tuskegee experiment, the Alabama study where hundreds of African-American men were told they were being treated for syphilis, but in fact were denied treatment. That U.S. government study lasted from 1932 until press reports revealed it in 1972.
The Guatemala experiment, which apparently ended in 1948, never provided any useful information. Records were hidden.
Reverby, who has written extensive about the Tuskegee experiments, found the evidence while conducting further research on Tuskegee.