Childhood malnutrition in Papua New Guinea has often been attributed to inadequate practices. Combining the methods of ethnography and nutrition, this study assesses the impact of beliefs and practices concerning breast feeding and supplementation on infant and toddler growth among the Amele of lowland Madang Province. Results indicate a clear role for notions about lactation and the proper timing of appropriate foods in growth retardation of young children. Conceptualizing developmental stages emically instead of etically is a useful approach to gathering data for nutrition education programs.