Forty-five healthy infants were included in a double-blind randomized prospective study comparing the nutritional value of two formulas. One group received a whey-predominant formula (n = 20); the other group received a whey hydrolysate formula (n = 25). Four infants of the whey hydrolysate group were dropped because they refused the formula. Although the mean daily volume intake was smaller with the whey hydrolysate formula compared with the whey-predominant formula (p < 0.001), the weight gain in the two groups after 13 weeks was identical (27.2 g/day in both groups; the mean difference in weight gain between the groups after 13 weeks was only 8 g). Length gain at 13 weeks was 10.4 cm in the whey-predominant formula group and 10.8 cm in the whey hydrolysate formula group (p = NS). After 13 weeks, blood was sampled for hemoglobin, hematocrit, red blood cell count, white blood cell count, lymphocytes, glycemia, proteins, albumin, prealbumin, calcium, phosphorus, urea, creatinine, iron, iron-binding capacity, zinc, and vitamins A and E. Except for the iron-binding capacity, zinc, urea (in plasma as well as in urine) (all three were higher in the whey hydrolysate group), no significant differences were found. According to these results, exclusive feeding of the whey hydrolysate formula from birth to 3 months of age to healthy infants appears to result in an adequate nutritional status, as assessed at 3 months of age.