Background:
Despite the importance of human immunodeficiency virus (HIV) transmission through heterosexual contact, the incidence of HIV infection in heterosexual cohorts has not been well studied, particularly in the developing world.

Objective:
To 1) determine the incidence of HIV infection in discordant heterosexual couples [couples in which one partner had HIV infection and the other did not] in Haiti and 2) assess risk factors for and methods of preventing HIV infection.

Design:
Prospective study.