Background. Optimal feeding of infants and young children in developing countries includes daily feeding of animal-source foods. Objective. To evaluate constraints on the availability of animal-source foods at the community level, access to animal-source foods at the household level, and intake of animal-source foods at the individual level among children under 3 years of age in case studies in five developing countries: Mexico, Peru, Haiti, Senegal, and Ethiopia. Methods. Data were obtained from published and unpublished research and from program experiences of health and agriculture specialists. Results. In Ethiopia, 27% to 51% of case-study children had consumed an animal-source food on the previous day; from 56% to 87% of children in the other case-study sites had consumed an animal-source food on the previous day. Data on intake of animal-source foods in grams were only available for the Latin American case-study sites, where daily milk intake was high in Mexico and Peru (195 and 180 g/day, respectively) and the intakes of meat, fish, and poultry (MFP) (29.0 and 13.6 g/day) and of egg (18.4 and 4.9 g/day) were low. The conceptual model guiding this work identified more constraining factors at the community and household levels than at the individual level. The most common constraints on feeding animal-source foods to young children were poverty, animal health, and land degradation at the community level; cost of animal-source foods and limited livestock holdings at the household level; and caregivers' perceptions of giving animal-source foods to children at the individual level. Conclusions. For program planning, it is useful to simultaneously consider factors that affect community availability of, household access to, and children's intake of animal-source foods. Efforts to overcome individual-level constraints on intake of animal-source foods should be coupled with activities to address community and household constraints. © 2007, The United Nations University.