Human immunodeficiency virus (HIV) infection is spreading rapidly in Haiti with HIV seroprevalence rates of 10% and 3% in urban and rural areas, respectively. Since 1985, heterosexual transmission has been the primary mode of acquisition of HIV. From 1981 to the present, the Cornell-GHESKIO unit in Port-au-Prince, Haiti, has developed the infrastructure to recruit and retain large cohorts of individuals at risk for HIV infection. Among the populations studied, couples discordant for HIV infection appear most suitable for eventual HIV phase III vaccine trial. This paper describes the recruitment, retention, and characteristics of the discordant-couples cohort, as well as the limitations of interventions aimed at behavior modification.