The purpose of this study was to examine the prevalence of antibody against hepatitis A (anti-HAV) in a population of homosexual men compared with that of heterosexual men in an area of intermediate HAV endemicity (Madrid, Spain). A total of 148 patients were recruited in a Sexually Transmitted Diseases Clinic: 74 homosexuals (mean age of 28 +/- 5 years) and 74 heterosexuals (29 +/- 5 years). The prevalence of anti-HAV antibody was 47% and 43% for homo- and heterosexuals, respectively. Among the factors evaluated (age, sexual orientation and practices, travel to high HAV endemicity areas) oral-anal contact was significantly associated with a higher prevalence of anti-HAV antibody (odds ratio, 2.8; 95% confidence interval, 1.1-7.4; P = 0.03). These results indicated that in an area of intermediate endemicity young homosexual men are not at increased risk of having acquired hepatitis A infection than heterosexuals. Oral-anal contact is an independent risk factor that influences the presence of anti-HAV antibody, regardless of sexual orientation.