Breast-fed infants grow less rapidly after the first 2 to 3 months of age than current standards. The DARLING study (Davis Area Research on Lactation, Infant Nutrition and Growth) was designed to evaluate whether this pattern should be considered "faltering" or is a normal outcome even under optimal conditions. Data on intake, growth, morbidity, activity, and motor development were collected longitudinally from infants who were breast fed for at least 12 months. Gross energy intake, calculated from 4-day records of milk and food intake at 3, 6, 9, and 12 months, averaged 91.4, 84.1, 86.7, and 91.8 kcal/kg per day, respectively, well below recommended amounts of metabolizable energy. Nevertheless, infants usually left some food unconsumed. Growth velocity was also below current reference data and was weakly correlated with energy intake. There were no significant negative associations between energy intake at any time and incidence, prevalence, or duration of any category of morbidity during the subsequent 3 months. There were no consistent associations between energy intake and activity level, time spent sleeping, or achievement of key developmental milestones. Similarly, infants with slower growth velocity were just as active and were ill no more often in subsequent months than infants who were growing more rapidly. Thus the deviation from current recommendations for energy intake and growth can be considered a normal pattern with no apparent deleterious consequences in our population of breast-fed infants.