Few practical guidelines exist on how to ensure that research participants in less-developed countries understand the consent form before enrollment. In a study of HIV-1 transmission in Haiti, participants were required to pass an oral examination on the contents of the consent form with a passing score of 12/15 (80%) before enrollment. 15 individuals were given information during a single meeting with a physician, and three (20%) passed. 30 subsequent volunteers were given information by a counsellor during three meetings, and 24 (80%) passed. Formal assessment of research participants' comprehension of the consent form should be considered as a routine step in the informed consent process in less-developed countries.