BACKGROUND: Zinc supplements reduce childhood morbidity in populations in whom zinc deficiency is common. In such populations, deficiencies in other micronutrients may also occur. OBJECTIVE: The objective was to determine whether the administration of other micronutrients with zinc modifies the effect of zinc supplementation on children's morbidity and physical growth. DESIGN: Two hundred forty-six children aged 6-35 mo with persistent diarrhea were randomly assigned to 1 of 3 groups to receive a daily supplement of 10 mg Zn alone (Zn; n = 81), zinc plus vitamins and other minerals at 1-2 times recommended daily intakes (Zn+VM; n = 82), or placebo (n = 83) for approximately 6 mo after the diarrhea episode ended. Morbidity information was collected on weekdays. Weight, length, and other anthropometric indicators were measured monthly, and plasma zinc and other indicators of micronutrient status were measured at baseline and 6 mo. RESULTS: Supplement consumption was high ( approximately 90%) in all groups, although slightly more vomiting was reported in the Zn+VM group (P < 0.0001, analysis of variance). The change in plasma zinc from baseline to 6 mo was greater in the 2 zinc groups (6.1, 27.3, and 16.2 micro g/dL in the placebo, Zn, and Zn+VM groups, respectively; P < 0.0001, analysis of variance). The Zn group had fewer episodes of diarrhea, dysentery, and respiratory illness and a lower prevalence of fever and cough than did the Zn+VM group and a lower prevalence of cough than did the placebo group (P = 0.05). No significant effects of supplementation on growth were observed. CONCLUSION: Morbidity was greater after supplementation with zinc plus multivitamins and minerals than it was after supplementation with zinc alone.