Interpretation of differences in serum vitamin A levels observed between Hispanic and non-Hispanic children may be complicated by confounding environmental factors. Data from the Mexican-American portion of the Hispanic Health and Nutrition Examination Survey and the second National Health and Nutrition Examination Survey were used to explore these differences in 4-11-y-old Mexican Americans and non-Hispanic blacks and whites before and after accounting for vitamin-mineral supplement use and poverty status. Initial differences in mean serum vitamin A levels and prevalences less than 20 micrograms/dL (0.70 mumol/L) or less than 25 micrograms/dL (0.87 mumol/L) among the three ethnic or racial groups were reduced or eliminated after accounting for the two descriptive variables. These results support the hypothesis that differences in serum vitamin A levels between Mexican-American and non-Hispanic children in the United States are due more to environmental factors than to ethnicity.