The nutritional and medical problems of 300 Mexican-American preschool children of migrant workers were evaluated in the spring of 1969 in Colorado. Outstanding in the history was the high infant mortality of 63 deaths per 1,000 live births. Frequent findings on physical examination included low height attainment, upper-respiratory tract infections, skin infections, dental caries, hypertrophied tongue papillae, and conjunctival folliculitis. Biochemical testing showed low vitamin A levels in 159 children, low alkaline phosphatase levels in 120 children, and low total serum proteins in 28 children. The relationship between nutritional and health problems was apparent in this study. Possible methods for improving the nutrition and health of the migrant children are discussed.