Risk factors for cervical infection with human papillomavirus (HPV) were assessed among 236 Italian women at risk for human immunodeficiency virus (HIV) infection (intravenous drug users (IVDU) or sexual partners of males at risk for HIV infection). All study participants underwent a structured interview, determination of HIV serostatus and detection of HPV cervical infection by means of polymerase chain reaction (PCR). Overall, the cervical presence of HPV DNA was ascertained in 86 of these 236 women (36.4%), while squamous intraepithelial lesions (SIL) were diagnosed in 57 (24.1%). HPV-infected and non-infected women did not differ in age, education and cigarette smoking. A statistically significant trend in the risk of HPV infection with increasing number of lifetime sexual partners was noted (P = 0.01), but such trend was attenuated in multivariate analysis (multiple logistic regression (MLR) odds ratio (OR) for > or = 20 partners vs 1 = 1.6, 95% confidence intervals (CI): 0.4-5.9). A nearly threefold higher risk of HPV cervical infection emerged among IVDU women (MLR-OR: 2.7, 95% CI: 1.4-5.0), and this difference was not influenced by HIV serostatus. The prevalence of HIV infection was higher among HPV-positive than HPV-negative women (62.8% and 54.0%, respectively) (MLR-OR = 1.9, 95% CI: 0.9-3.8), and the proportion of women with less than 200 CD4+ cells/mm3 was slightly and not significantly higher among HPV-positive (47.1%) than negative women (37.2%).