Zinc is an essential nutrient for growth and low intake can result in growth retardation. However, high zinc intake can affect copper metabolism. Therefore, data from a study of 10 male premature infants fed a cow's milk-based formula nonfortified with zinc (mean +/- SD = 1.4 +/- 0.1 mg X l-1) were compared with data of 10 similar infants fed the same formula fortified with zinc (4.1 +/- 0.3 mg X l-1). Growth, food intake, zinc and copper nutritional status were studied from 6 through 122 days of age. No differences in gain of weight, length and head circumference and in food intake were found. Serum zinc concentration was significantly (p less than 0.05) and hair zinc concentration was slightly higher in the infants fed the zinc-fortified formula at 122 days of age. Copper and ceruloplasmin concentrations in serum and hair copper concentration were similar in both groups at 122 days of age. The results suggest that feeding a formula nonfortified with zinc did not affect growth of male premature infants. Feeding a zinc-fortified formula on the other hand had no influence on copper nutritional status.