Do mothers of undernourished children recognize their offspring's needs? How do they feed these target children compared to other households members when food supplements are available? Which cultural principles of intra-household food distribution are associated with feeding behavior? How do household members perceive and use food supplements that are donated for undernourished target children? Answers were sought in a dietary-ethnographic study of 45 households receiving supplements for a low-weight child between one and five years, of age in two periurban low-income communities of the City of Guatemala. The central hypothesis was that we would find four cultural principles of food distribution: contributions, need, equity, and demand. The dietary survey combined direct measure and recall techniques and was done twice for all 230 individuals conforming these households. Ethnographic interviews were carried out with mothers of all target children. T-tests determined the relation between food distribution behavior and cultural rules. Findings revealed that the cultural principles of contributions, needs, and demand are present, but instead of the equity principle, we found one of equality. In the great majority of the feeding events observed, the child's mother prepares and distributes the food. The target child does not receive preferential treatment in the intra-household distribution of food supplements and other foodstuffs. Donated milk is destined principally for the children in the household; all other supplements are distributed among all members. Adult males are favored in the distribution of kcal at regular mealtimes. Children are favored in the distribution of kcal when total daily consumption is calculated. There are significant associations between the expressions of the cultural principle favoring equal distribution and that of contribution which favors adult men, and actual food distribution behavior. These principles seem to operate at formal meal events only. It was found that feeding behavior between meals (snacks, nibbling, etc.) is not subject to these salient principles and tends to compensate those household members who are not given preferential treatment in food distribution at formal mealtimes.