Highly active antiretroviral therapy (HAART) has improved HIV prognosis, but its effect on cervical intraepithelial neoplasia (CIN), which is associated with HIV, is uncertain. Among 71 HAART-treated women the prevalence of CIN before HAART was 55%. After a median of 10 months after starting HAART the prevalence had increased to 62% (P = 0.20); 13% of patients experienced regression of a CIN lesion, and this was most strongly associated with a greater increase in CD4 cell count. Such studies will provide the basis for guidelines for monitoring CIN in HIV-positive women in the HAART era.