Background: Many people infected bg human immunodeficiency virus (HIV) acquire severe cytomegalovirus (CMV) diseases. Factors associated with CMV seropositivity are poorly documented in sexually active HIV-infected men. Goal: To study CMV seroprevalence in HIV-infected men according to sexual behavior before the diagnosis of HIV seropositivity. Study Design: Cross-sectional study. CMV seroprevalence was studied at enrollment in a prospective cohort of homosexual and heterosexual men infected by HIV through sexual contact. Results: In the study population (n = 723), age, sexual preference, previous lifetime history of sexually transmitted diseases, and multiple sexual partners were independently related to CMV seropositivity. Furthermore, routine condom use during the fi months before diagnosis of HIV seropositivity was significantly related to CMV seropositivity; (adjusted odds ratio [OR]: 0.4, 95% confidence interval [CI]: 0.1-1.0), occasional condom use being of borderline significance [adjusted OR: 0.5, CI: 0.2-1.3]. Conclusions: This study confirms the importance of sexual factors in the acquisition of CMV infection by HIV-infected men and suggests a protective effect of condom use.