The reliability of self-reports of sexual behaviors related to HIV transmission was examined in a study of homeless men with severe mental illness. Thirty-nine patients of a New York City shelter psychiatric program were interviewed about their sexual behaviors in the past six months. The same interview was administered twice, with a one-two-week internal between interviews. Test-retest reliability was assessed using kappa and intra-class correlation coefficients. Reliability was lower for condom use. The authors conclude that reliable self-reports about sexual behavior can be obtained from homeless men with severe mental illness. (Authors)