Understanding the natural history of sexually transmitted infections requires the collection of data on sexual behavior. However, there is concern that self-reported information on sexual behavior may not be valid, especially if study participants are culturally and linguistically distinct. The authors completed a test-retest reliability study of 1,069 men recruited in Brazil, Mexico, and the United States in 2005 and 2006. All of the men completed the same computer-assisted self-interview approximately 3 weeks apart. Refusal rates, kappa coefficients, and intraclass correlation coefficients were calculated for the full sample and by country, age, and lifetime number of female sex partners. Reliability coefficients for each study site and the combined population were high for almost all questions. With few exceptions, the authors found high test-retest reliability with a computer-assisted self-interview on sexual behavior used in 3 culturally and linguistically distinct countries.