Do parents invest more in higher quality children, or do they compensate for lower quality by giving more to children with lower endowments? We answer this question in the context of a large-scale iodine supplementation program in Tanzania. We ?nd that children with higher program exposure were more likely to receive necessary vaccines and were breastfed for longer. Siblings of treated children were also more likely to be immunized. Fertility behavior and investments at the time of birth were unaffected, suggesting that parents reactedto observed endowment changes rather than indirect program effects.