The duration of pneumonia and of diarrhea is reported to be longer in HIV-infected than in uninfected children. We assessed the effect of a multi-micronutrient supplement on the duration of hospitalization in HIV-infected children. In a double-blind, randomized trial, HIV-infected children (4-24 mo) who were hospitalized with diarrhea or pneumonia were enrolled (n = 118) and given a daily dose of a multi-micronutrient supplement (containing vitamins A, B complex, C, D, E, and folic acid, as well as copper, iron, and zinc at levels based on recommended daily allowances) or a placebo until discharge from the hospital. Children's weights and heights were measured after enrollment and micronutrient concentrations were measured before discharge. On recovery from diarrhea or pneumonia, the children were discharged and the duration of hospitalization was noted. Anthropometric indices and micronutrient concentrations did not differ between children who received supplements and those who received placebos. Overall, the duration of hospitalization was shorter (P < 0.05) among children who were receiving supplements (7.3 ± 3.9 d) (mean ± SD) than in children who were receiving placebos (9.0 ± 4.9); this was independent of admission diagnosis. In children admitted with diarrhea, the duration of hospitalization was 1.6 d (19%) shorter among children receiving supplements than in those receiving placebos, and hospitalization for pneumonia was 1.9 d (20%) shorter among children receiving supplements. Short-term multi-micronutrient supplementation significantly reduced the duration of pneumonia or diarrhea in HIV-infected children whowere not yet receiving antiretroviral therapy and who remained alive during hospitalization.