To evaluate the humoral immune response to human papillomavirus (HPV) in women infected with human immunodeficiency virus (HIV), serum samples of 83 HIV-positive individuals were analysed by ELISA for specific antibodies of the isotypes IgG, IgA and IgM recognizing HPV-6, -11, -16, -18 and -31 L1 virus-like particles (VLPs). Papillomavirus-related lesions were present in 30 of 83 HIV-positive women. Twenty-one women (25%) presented with high-/intermediate-grade anogenital squamous intraepithelial lesions. PCR analysis and sequencing for HPV typing was done from biopsy specimens of 18 women; PCR-positive results were obtained in 90% of cases. In addition, HPV DNA hybrid capture assays were performed from cervical swabs of 58 HIV-positive women, 53% of whom had a positive result for high-risk HPV. Overall, positive IgG reactivity to HPV-6/-11 and HPV-16/-18/-31 was seen in 19%/31% and 49%/30%/24% of HIV-positive women, respectively. HPV-seropositivity was even higher than in 48 HIV-negative cervical intraepithelial neoplasia/cancer patients with percentages as follows: 8%/2% and 31%/15%/15%. This difference was significant for HPV-16 (P=0.046). IgA responses were comparable to IgG. IgM responses were low. The extraordinarily high rate of antibodies to the capsid protein L1 of high-risk HPVs (HPV-16, -18 and/or -31) in 58% of HIV-positive women compared to 19% (P=0.00001) of 102 healthy HIV-negative control women suggests a high lifetime cumulative exposure to HPV and increased expression of capsid proteins due to cellular immunodeficiency in HIV-infected women.