We compared the growth, biochemical status, and mineral status of 30 very-low-birth-weight infants randomly assigned to receive preterm human milk (Group I, 10 infants) from their own mothers, fortified preterm human milk (Group II, 8 infants), or a high-caloric-density premature formula (Group III, 12 infants). Added to the infant's own mother's milk, a human milk fortifier at full strength provided additional protein (60:40 whey/casein, 0.7 g/dl), calories (4 kcal/oz), and minerals. Volume of intake, feeding tolerance, and complications were similar in the three groups. Infants receiving fortified preterm human milk showed growth, biochemical status, and mineral status similar to those receiving high-caloric-density formula, but infants receiving fortified preterm human milk grew faster (12.0 +/- 3.2 vs. 8.9 +/- 1.1 days/300 g, p less than 0.05), had higher serum protein (4.6 +/- 0.5 vs. 4.2 +/- 0.2 g/dl, p less than 0.05), and tended to have better mineral status (higher serum calcium, lower alkaline phosphatase, and higher serum phosphorus, none individually significant) than infants receiving preterm human milk alone. This study supports previous observations that fortified preterm human milk provides nutritional advantages for very-low-birth-weight infants.