Mucocutaneous diseases are common in HIV-infected patients. The aim of the present study was to determine the observed frequency of skin diseases and their prognostic significance for the progression of HIV infection. In a cohort of 150 HIV-infected patients diagnosed from 1986 to 1987 the number of mucocutaneous diseases, the CD4+ cell count, time to development of AIDS and survival time were registered for a period of 5 years. Eight patients were lost for follow-up. In the remaining 142 patients the number of mucocutaneous findings increased markedly during the observation period. The most frequent registered diseases and these with the highest increase were oral candidiasis, hairy leukoplakia, seborrhoeic dermatitis and herpes simplex. On average, 5.2 different diagnoses were registered per patient at the end of the follow-up period. The study showed that the total number of mucocutaneous diseases and the CD4+ cell count were significantly correlated to survival time and time to development of AIDS. The number of mucocutaneous diseases, like the CD4+ count, is an indicator of the immune system and the prognosis of HIV infection.