Background: Human papillomavirus (HPV) causes anal intraepithelial neoplasia (AIN) in HIV-seropositive men. The detection of HPV genotypes in anal biopsies and swabs was compared. Methods: HPV DNA was detected in anal swabs and biopsies obtained concurrently from 154 HIV-seropositive men [31 without AIN, 60 low-grade AIN (AIN-1), 62 high-grade AIN (AIN-2,3), and 1 indeterminate AIN] under or eligible to highly active antiretroviral therapy. Results: HPV DNA was detected in 24.2% of normal biopsies compared with 93.5% with AIN-2,3 (P < 0.001) and 88.3% with AIN-I (P < 0.001). The proportion of biopsies containing multiple genotypes was greater in AIN-1 (n = 21, 35.0%; P = 0.002) and AIN-2,3 (n = 38, 58%; P < 0.001) than in normal biopsies (n = 2, 6.5%). The most frequent genotypes in order of frequency were in AIN-2,3 biopsies HPV-16, 18, 58, and 45 and were in AIN-1 biopsies HPV-6, 11, 16, and 39. Controlling for age, CD4 count, and smoking, the presence of high-risk HPV DNA in biopsies [odds ratio (OR) = 50. 8, 95% confidence interval (CI): 13.0 to 199.5] but not in swabs (OR = 2.0, 95% CI: 0.6 to 7.0) was associated with AIN-2,3. Conclusions: AIN-2,3 was associated with high-risk HPV infection detected in biopsies but not in swabs in men under or starting highly active antiretroviral therapy, possibly due to the presence of HPV foci outside of the neoplastic lesion.