In order to identify virulent types of Escherichia coli 50 samples were obtained from the faeces of HIV-positive patients some of which showed signs of AIDS. Genotypic identification was performed hy colony hybridization using DNA probes. We observed: 16 (32%) toxigenic samples, 8 had thermolablile toxin and 8 with thermostable toxin; 8 samples were enteropathogenic, 4 of which had localized adhesiveness and 4 diffuse adhesiveness; 31 (62%) samples had unidentified E. coli. We found no direct correlation between the virulent type established by us and the antecedent of diarrhea or enteritis. Virulent types were more frequent (70.8 %) in stages II and IV of the "IV infection.