Using a sample of 678 HIV-seronegative women, we measured self-reports of HIV-related cognitions, specifically knowledge, perceived exposure risks, and outcome expectations. We also ascertained prevalent and incident bacterial STDs and measured self-reports of behavioral risk reductions. We tested for associations between (a) cognitions and STD prevalence, (b) cognitions and incident STDs, (c) cognitions and behavioral risk reductions, and (d) risk reductions and incident STDs. Symptom knowledge was associated with lower prevalence, but not incidence. Beliefs in the efficacy of risk reductions showed a protective effect against incident STDs. Perceived exposure risk and symptom knowledge were associated with risk reduction behavior.