Objective: We examined whether supplementation with vitamin A and/or vitamins B, C, and E to HIV-infected women during pregnancy and lactation is related to increased concentrations of vitamins A, B12, and E in their infants during the first 6 months of life. Design: We carried out a randomized clinical trial among 716 mother-infant pairs in Dar-es-Salaam, Tanzania. Women were randomly allocated to receive a daily oral dose of one of four regimens: vitamin A, multivitamins (B, C, and E), multivitamins including A, or placebo. Supplementation started at first prenatal visit and continued after delivery throughout the breastfeeding period. The serum concentration of vitamins A, E and B12 was measured in infants at 6 weeks and 6 months postpartum. Results: Maternal vitamin A supplementation increased serum retinol in the infants at 6 weeks (mean difference ¼ 0.09 mmol/l, Po0.0001) and 6 months (mean difference ¼ 0.06 mmol/l, P ¼ 0.0002), and decreased the prevalence of vitamin A deficiency, but had no impact on serum vitamins E or B12. Multivitamins increased serum vitamin B12 at 6 weeks and 6 months (mean differences ¼ 176 pmol/l, Po0.0001 and 127 pmol/l, Po0.0001, respectively) and vitamin E (mean differences ¼ 1.8 mmol/l, P ¼ 0.0008 and 1.1 mmol/l, P ¼ 0.004, respectively) and decreased the prevalence of vitamin B12 deficiency. Conclusions: Vitamin supplementation to HIV-1-infected women is effective in improving the vitamin status of infants during the first 6 months of age.