Our objective in this trial was to assess the impact of daily zinc supplementation on growth in young children. A double-blind, randomized, placebo-controlled trial was conducted in New Delhi, India. We enrolled 2482 children aged 6-30 mo who were supplemented daily with placebo or zinc (10 mg elemental zinc to infants and 20 mg to older children) for 4 mo. At enrollment, all children also received a single dose of vitamin A (104.7 micromol for infants and 209.4 micromol for older children). Weight and length were measured at enrollment and 4 mo later. Weekly visits were conducted by field workers to ascertain morbidity in the previous 7 d. Change in length, weight, length-for-age Z-scores (LAZ), and weight-for-length Z-scores (WLZ) after 4 mo of supplementation were assessed in the zinc and placebo groups. After 4 mo of supplementation, the weight and length gains in the 2 groups did not differ and there was no impact on LAZ, weight-for-age, and WLZ in the 2 groups. There was no substantial effect in any of the subgroups defined for age, income, gender, zinc levels in the crude analysis nor after adjusting for age, gender, income, breast-feeding status, and baseline anthropometric status. Despite successful zinc supplementation reflected in increased plasma zinc concentration and a substantially reduced incidence of diarrhea and pneumonia in zinc-supplemented children, the intervention did not have a beneficial effect on growth.