Fifteen fullterm female infants were enrolled in each of two feeding groups and all but one completed the proposed period of observation to age 112 days. Formulas prepared from the same ingredients (fat-free milk solids, a mixture of corn and coconut oils, lactose, vitamins and minerals) were fed ad libitum to both groups. Formula concentration was 54 kcal/100 ml for one group and 100 kcal/100 ml for the other. A limited selection of commercially prepared strained foods was permitted after 28 days of age. Weighed intakes of food were recorded for each day of study. During the internal 8 through 41 days of age, the infants fed the 54 kcal/100 ml formula consumed a considerably greater quantity of food but fewer calories than did those fed the 100 kcal/100 ml formula. Those fed the 54 kcal/100 ml formula also gained less weight. These differences between feeding groups were statistically significant. After 41 days of age, mean caloric intakes (kcal/kg/day) and rates of gain in weight were similar for the two feeding groups. The data provide a basis of speculation on the possible difference in allocation of calories to growth and non-growth in the two groups.