SummaryOf 178 normal breastfed infants enrolled during the first 9 days of life, 129 (59 males and 70 females) completed the planned period of observation to 112 days of age. Limited amounts of formula and beikost were permitted and intakes of these foods were determined. Length and weight were measured at standardized ages and blood for serum chemical determinations was obtained.Data from this study were combined with similar data published (1) previously. Thus, data are now available concerning 117 males and 116 females. Means, standard deviations and percentile values, including 5th and 95th percentile values, for length and weight at. tained and for rates of gain in length and weight between various ages are presentedMeans and percentile values for intake of calo. ries from formula and beikost and for serum chemical values are presented. In instances where analysis of variance indicated statis. tically significant effects of age and/or sex serum chemical values have been tabulated or an age‐ and/or sex‐specific ba