OBJECTIVE: To estimate the efficacy of isotretinoin for prevention of progression of low-grade squamous intraepithelial lesions (SIL) of the cervix to high-grade lesions or invasive cervical cancer; to estimate the regression rate of low-grade SIL with isotretinoin and the toxicity of isotretinoin in this setting; and to correlate serum CD4 levels with progression of low-grade SIL. METHODS: A randomized, phase III, observation-controlled, multicenter trial was performed in which 117 human immunodeficiency virus (HIV)-positive women with low-grade SIL of the cervix received either oral isotretinoin at 0.5 mg/kg per day for 6 months or observation. Papanicolaou smears and colposcopy/biopsy were done at regular intervals during follow-up. The primary endpoint was progression to high-grade SIL or cervical cancer. RESULTS: Twenty-one of 102 women (20.6%) completing follow-up experienced progression to high-grade SIL, 13 in the observation group and eight in the isotretinoin group. This difference was not significant (P = .29). No cases of invasive cancer were seen. Baseline CD4 levels were lower than anticipated (median 329 cells/mm3), but not associated with time to progression (P = .36). Most subjects (63 of 102, 61.7%) used highly active antiretroviral therapy. Subjects under age 30 were more likely to progress than those older than 30 (P = .046). CONCLUSION: Isotretinoin was not associated with longer time to progression of low-grade SIL. This appears to be a chronic condition in HIV-positive women, with a low risk of progression and significant rate of resolution. As in the general population, observation without excisional therapy may be appropriate for HIV-positive women with low-grade SIL.