BACKGROUND AND OBJECTIVES: The presence of sexually transmitted infections (STIs) may facilitate transmission of HIV to uninfected partners. GOAL: To describe the incidence of reinfection with Trichomonas vaginalis in HIV-infected women and to assess predictors of reinfection. STUDY DESIGN: A retrospective cohort study using data abstracted from medical records of HIV-infected women with at least one diagnosis of trichomoniasis. RESULTS: Approximately one third (36%) of the study population was reinfected with T vaginalis during the follow-up period, with an incidence of 16.4 reinfections per 100 person years. Significant predictors of reinfection included history of another STI (hazard ratio, 1.52; 95% CI, 1.08-2.14) and becoming pregnant during the follow-up period (hazard ratio, 0.59; 95% CI, 0.39-0.87). CONCLUSIONS: There is a high rate of reinfection with T vaginalis in HIV-infected women. Further research that includes information on sexual partners should be conducted to better describe the reinfection patterns of trichomoniasis.