During recovery from severe wasting, malnourished children gain weight at greatly accelerated rates. To determine if additional zinc added to their basal therapeutic diets increased the retention of lean tissue and stimulated protein metabolism, we studied three groups of children taking either the basal diet alone or the basal diet supplemented with either 76 mumol (5 mg) or 153 mumol (10 mg) Zn/kg diet. The zinc-supplemented children gained similar weight and consumed the same amount of diet as the unsupplemented children. Zinc supplementation resulted in a greater net absorption of nitrogen and a higher rate of protein turnover, as estimated from urinary ammonia 15N enrichment after oral [15N]glycine. We conclude that additional zinc affected the composition of newly synthesized tissue and intermediary nitrogen metabolism.