OBJECTIVE To describe the incidence of, and risk factors for, Mycobacterium avium intracellulare complex (MAC) infection in HIV-infected children. SETTING University-affiliated children's hospital. DESIGN AND METHODS The medical records of 70 HIV-infected infants and children were reviewed retrospectively. RESULTS Seven children (10% of the HIV-infected patients; 18% of those with AIDS) developed disseminated MAC (dMAC). An additional seven children had gastrointestinal colonization with MAC. Risk of dMAC was associated with increasing age, decreasing CD4 cell count, and (possibly) long-term steroid therapy. CONCLUSIONS HIV-infected children are at risk of developing dMAC. Children older than 60 months and those with a CD4 cell count < 100 x 10(6)/l are most at risk.