A serosurvey of United States military personnel presenting to a sexually transmitted diseases (STD) clinic or reporting for routine physical examination in the Philippines was conducted to determine the risk factors for hepatitis B (anti-HBc), hepatitis C (anti-HCV), and cytomegalovirus (anti-CMV) infection. Among 470 male study subjects, 74 (15.7%) were positive for anti-HBc, five (1.1%) were positive for anti-HCV, and 232 (49.4%) were positive for anti-CMV. A history of a STD (odds ratio [OR] = 7.7) and contact with a female prostitute (OR = 2.3) were significantly associated with anti-HBc seropositivity after adjusting for age, race/ethnicity, foreign birth, and classification as either a STD or routine examination patient. Anti-CMV seropositivity was significantly associated with a history of a STD (adjusted OR = 2.0). These data suggest that in this military population, heterosexual activity was a risk factor for acquiring hepatitis B and CMV infection. United States military personnel stationed in high-risk areas of the western Pacific, particularly patients presenting to STD clinics, may need to be targeted for hepatitis B vaccination.