The aim of the study was to determine the incidence of tuberculosis in newly diagnosed HIV-infected children and to determine whether anti-tuberculosis prophylaxis is indicated. We prospectively investigated newly diagnosed HIV-infected children for tuberculosis during the period June 1995 untill September 1996. A chest X-ray and a Mantoux test were done in all children. The Mantoux test was correlated with a skin test for Candida. Gastric aspirates were obtained from all children and sent for M. tuberculosis culture. There were 75 children in the study group. The mean age was 13.8 months. According to the CDC classification for HIV-infection, 37% of children were in the B3 category. The common clinical problems were as follows: Bronchopneumonia-58%; candidiasis-36%, hepatosplenomegaly and lymphadenopathy-39%; and marasmus 18%. Tuberculosis was diagnosed in 22% of children. Seven children had positive cultures on gastric aspirates for M. tuberculosis and eight children had chest X-rays highly suggestive of pulmonary tuberculosis. Two children had unproven tuberculosis, but responded dramatically to anti-tuberculosis therapy. In conclusion, the indidence of tuberculosis in newly diagnosed HIV-infected children was unexpectedly high(22%). This can probably be explained by the high incidence of tuberculosis in South Africa. The recommendation is that newly diagnosed HIV-infected children in our setting receive anti-tuberculosis prophylaxis.