Objective: To estimate changes in high-risk women's knowledge of cervical cancer prevention, human papillomavirus (HPV), and HPV vaccination since introduction and marketing of HPV vaccines. Methods: At study visits in 2007 and 2008-2009, women with the human immunodeficiency virus (HIV) and at-risk comparison women in a multicenter U.S. cohort study completed 44-item self-report questionnaires exploring their knowledge of cervical cancer prevention, HPV, and HPV vaccination. Results from 2007 were compared with those obtained in 2008-2009. Knowledge scores were correlated with demographic variables, measures of education and attention, and medical factors. Significant associations were assessed in multivariable models. Results: HIV-seropositive women had higher knowledge scores than seronegative women at baseline (13.2±5.7 compared with 11.8±6.0, P<.001) and follow-up (14.1±5.3 compared with 13.2±5.5, P=.01), but the change in scores was similar (0.9±5.3 compared with 1.5±5.5, P=.13). Knowledge that cervical cancer is caused by a virus rose significantly (P=.005), but only to 24%. Belief that cervical cancer is preventable only rose from 52% to 55% (P=.04), but more than 90% of women in both periods believed regular Pap testing was important. In analysis of covariance models, higher baseline score, younger age, higher education level, higher income, and former-as opposed to never-drug users, but not HIV status, were associated with improved knowledge. Conclusion: High-risk women's understanding of cervical cancer and HPV has improved, but gaps remain. Improvement has been weakest for less educated and lower-income women.