Rural to urban migration has increased greatly over the last several decades in Latin America. New migrants usually live in peri-urban communities that lack basic services, including potable water, sewerage or electricity. Residents of one such community near Lima, Peru, were found to have a high rate of infant and childhood mortality; half of childhood deaths were associated with diarrhea. Surviving children had a high rate of diarrhea with a peak incidence in 12 to 23-month-old children, Young children had mean weights and lengths at birth that were nearly identical to North American newborns (NCHS population), and growth during the first few months was similar to the reference population. However, relative growth faltering was observed after the first four months of life suggesting that environmental factors, either nutrition or infectious diseases, were interfering with potential growth. After this preliminary study, longitudinal investigations of the feeding practices, dietary intake and diarrheal diseases of infants were undertaken in order to design rational programmatic interventions to improve the nutritional well-being of children in this and similar communities. © 1987, Taylor & Francis Group, LLC. All rights reserved.