Abstract. To what extent can young adult children rely on their parents for financial support? This question will take on added importance if the commitments of the Social Security system put greater strain on the children of retirees. Despite the critical role that parents have in supporting their children, why they help some and not others remains unclear. Findings using two waves of data from the Health and Retirement Study that control for the needs of children and the resources of parents suggest that parents give more inter vivos financial assistance to their disadvantaged children rather than focusing on children most able to give financial help in return. Other measures of child well-being besides income, including home ownership, education, parental status, and marital status, also suggest that parents help needier children more. Children who live nearby also receive more, a finding consistent with exchange motives or simply the ability of these children to more stridently demand support. Neither altruism nor exchange theories explain why stepchildren receive substantially less support than naturally born or adopted children. The diversity of effects suggests that giving is based on heterogeneous motives—parents may temper their altruism for children by the degree to which they feel responsible and by the stridency of some children in seeking support. Findings are robust upon allowing for unobserved differences across families by estimating fixed effect models.