The selenium in the diet of persons in arsenic-endemic areas, high levels of arsenic in the drinking water, was evaluated. The methodology used was that of 24-hr dietary recall. Daily selenium intakes of two rural towns in northern Mexico were found to be similar, approximating 72.9 and 60.6 micrograms. These values were similar to those of a previously arsenic-exposed area from California, Edison community. The Edison participants had a daily selenium intake of 61.8 micrograms. The possible negative effect of selenium to produce differences in reported geographical variation in disease could not be substantiated in this study. Other nutrient intakes, protein and energy were also found similar for communities. Differences were noted in vitamin A intake where one-third the daily requirement was experienced by Mexican participants compared to two-thirds the requirement being satisfied by those participants from Edison.