We investigated the association between Buruli ulcer and HIV by comparing the HIV-1/2 seroprevalence in a series of 426 Buruli ulcer patients and a sample of 613 residents of southern Benin. The overall HIV prevalence was 2.6% (11/426) among patients and 0.3% among controls (2/613), giving an odds ratio for the association between HIV and Buruli ulcer of 8.1 (95% confidence interval = 1.8-75; P = 0.003).