This study examined whether past grandparental child care is related to present support from adult children. On the basis of social exchange theory, the authors expected that grandparental child care creates a debt that is repaid in the form of receiving support later in life. Using data from the Longitudinal Aging Study Amsterdam (N = 349 parents, N = 812 adult children), the authors found that grandparents who frequently provided child care for sons in the past more often received instrumental and emotional support from these sons approximately 13 years later than grandparents who less frequently provided child care. Investments in daughters did not pay off. Instrumental support other than child-care provision did not predict receiving support from either sons or daughters, but emotional support did. These results support the notion of long-term reciprocity in parent-child relationships, but its importance depends on the child's gender and the type of earlier investment.