OBJECTIVE: To estimate the accuracy of Pap testing for women who are human immunodeficiency virus (HIV)-seropositive, with a focus on negative predictive value. METHODS: Participants in the Women's Interagency HIV Study were monitored with conventional Pap tests every 6 months. After excluding those with abnormal Pap test results before study, cervical disease, or hysterectomy, women with negative enrollment Pap test results were monitored for development of precancer within 15 or 39 months, defined as a Pap test result read as high-grade squamous intraepithelial lesion, atypical glandular cells favor neoplasia, or adenocarcinoma in situ, or a cervical biopsy read as cervical intraepithelial neoplasia 2 or worse. Correlations between one or more consecutive negative Pap test results and subsequent precancer were assessed using Cox proportional hazards models. RESULTS: Among 942 HIV-infected women with negative baseline Pap test results, eight (1%) developed precancer within 15 months and 40 (4%) within 39 months. After three consecutive negative Pap test results, precancer was rare, with no cases within 15 months and 10 of 539 (2%) within 39 months. No women developed precancer or cancer within 39 months after 10 consecutive negative Pap test results. Risks for precancer within 15 months after negative Pap test result included current smoking (adjusted hazard ratio [HR] 1.5, 95% confidence interval [CI] 1.2-2.0 compared with nonsmokers), younger age (adjusted HR 1.5, 95% CI 1.1-2.1 for women aged younger than 31 years compared with older than 45 years), and lower CD4 count (adjusted HR 11.8, 95% CI 1.3-2.3 for CD4 200-500/microliter, adjusted HR 2.2, 95% CI 1.6-2.9 for CD4 less than 200/microliter, compared with CD4 more than 500/microliter). CONCLUSION: Annual Pap testing appears safe for women infected with HIV; for those with serial negative tests, longer intervals are appropriate.