Anemia is among the most widespread health problems for children in developing countries. This paper evaluates the impact of a randomized health intervention delivering iron supplementation and deworming drugs to Indian preschool children. At baseline, 69 percent were anemic and 30 percent had intestinal worm infections. Weight increased among assisted children, and preschool-participation rates rose by 5.8 percentage points, reducing absenteeism by one-fifth. Gains were especially pronounced for those most likely to be anemic at baseline. Results contribute to a growing view that school-based health programs are an effective way of promoting school attendance in less developed countries.