The results of a study on onychomycosis in AIDS related complex and AIDS patients presenting for dermatology consultation at an infectious diseases department are reported. The clinical results showed that most patients presented a proximal white superficial onychomycosis. The association with a clinical interdigital involvement was rare, but the association with a mycotic plantar keratoderma was more frequent. The laboratory results showed that dermatophytes were the most frequent etiologic agents, especially Trichophyton rubrum (58%). Although most of these patients presented an oral candidiasis, Candida albicans was isolated only in seven patients' nails. Surprisingly, Pityrosporum ovale was the only etiologic organism that was found in two patients. This result was confirmed with a histologic examination.