OBJECTIVE This study was designed to assess the significance of HIV-related oral lesions in predicting the rate of progression to AIDS. METHODS Cohorts were investigated prospectively, and oral examinations were performed by clinicians trained in the diagnosis of oral lesions. METHODS We studied three existing cohorts of homosexual and bisexual men in San Francisco, California, USA. METHODS Of the HIV-infected men who received standardized oral examinations (n = 791), 603 were eligible for analysis of baseline examinations and 448 for analysis of follow-up examinations. METHODS We determined time from presence of oral lesion at baseline or follow-up examination, or from participant self-reported history of the lesion, to diagnosis of AIDS. RESULTS Using proportional hazard regression and stratifying by CD4 lymphocyte count at the time of baseline oral examination, we found that the rate of development of AIDS was increased among men with hairy leukoplakia [relative hazard, 1.8; 95% confidence interval (CI), 1.2-2.7], oral candidiasis (relative hazard, 7.3; 95% CI, 3.1-17.3), and both lesions (relative hazard, 3.1; 95% CI, 1.6-6.1) compared with men with normal findings. On follow-up examination, stratifying for CD4 count, the rate of progression to AIDS was similar for those with hairy leukoplakia compared with those with oral candidiasis. The progression rate from oral candidiasis to AIDS was faster from presence on baseline examination than from presence on follow-up examination or from self-reported history of the lesion. CONCLUSIONS The presence of oral candidiasis and/or hairy leukoplakia on baseline examination confers independent prognostic information and should be incorporated into HIV-staging schemes.