The growth of 238 healthy full-term infants was followed under a carefully monitored nutritional protocol during the first year of life. The infants were weaned at different ages either to a proprietary infant milk formula or to a home-prepared cow's milk formula. Solid foods were introduced at 3.5 months of age. The 56 infants who were breast-fed for a period of at least 6 months were compared to infants weaned prior to one month of age to one of the two milk regimens. In the breast-fed infants, the weight, weight-for-height-age, and skinfold thickness were similar to values in the proprietary formula-fed infants but were lower than the corresponding values in the cow's milk-fed infants at 6 months of age and subsequently. By using weight-for-height-age as a criterion, no obesity was found among any of the 238 infants, and only 1.7% were considered to be overweight. The results indicate that present recommendations for infant feeding in Finland--including prolonged breast feeding, the use of proprietary milk formulas after weaning, and later introduction of solid foods--prevent overnutrition.