The objective of this study was to compare acute and chronic undernutrition rates before and after the introduction of a food-supplementation program as an adjunct to routine health care for children of migrant workers in the Dominican Republic. The cross-sectional study was conducted in five rural communities in the Dominican Republic. Children 18 years and younger were eligible if they received routine health care from local mobile clinics. Data were obtained before (2005) and after (2006) initiation of a food-supplementation program. chi(2) or Fisher exact tests were used for analysis. Among 175 children in 2005, 52% were female, and 59% were < 5 years of age (mean age = 5.3 years). Among 148 children in 2006, 48% were female, and 57% were < 5 years of age (mean age = 5.6 years). Acute undernutrition rates decreased from 40% to 23% (P = 0.001) after initiation of the food-supplementation program. Rates of chronic undernutrition decreased from 33% to 18% after the initiation of the food-supplementation program (P = 0.003). Food supplementation in the context of routine health-care visits improved the nutritional status of children, and it warrants further exploration as a way to reduce childhood undernutrition in resource-scarce areas.