Risk factors for postcoital bleeding were examined in 475 women who were enrolled in a study of heterosexual transmission of human immunodeficiency virus (HIV). In bivariate analyses, history of sexually transmitted diseases (STDs; P = .03), HIV infection (P = .008), and dyspareunia or pain during intercourse (P = .0001) were significant risk factors. In multivariate analysis, the two latter factors remained significant (for HIV, odds ratio [OR] = 2.1, P = .02, 95% confidence interval [CI] = 1.1-4.0; for dyspareunia, OR = 3.5, P < .001, 95% CI = 1.8-6.6), as did the interaction term of STD history and heavy smoking (OR = 2.4, P = .02, 95% CI = 1.2-5.0). Pain during intercourse was the strongest predictor of postcoital bleeding but may be part of the same phenomenon. Similarly, because this study relied on cross-sectional data, the direction of the causal pathway linking HIV to postcoital bleeding cannot be established. However, these data suggest that smoking, a modifiable risk factor, may increase risk of postcoital bleeding and contribute to susceptibility for HIV and other STDs.