OBJECTIVE: Relatively little is known about the intergenerational mechanisms that lead to social disparities in child health. We examined whether the association between low socioeconomic status (SES) and child behavior problems is mediated by maternal health conditions and behavior. METHODS: Prospective cohort data (1979-1998) on 2,677 children and their mothers were obtained from the National Longitudinal Survey of Youth. SES, the Child Behavior Problems Index (BPI), and maternal smoking, depressive symptoms, and alcohol use before, during, and after pregnancy were examined. RESULTS: Lower income and lower maternal education were associated with increased child BPI scores. Adjustment for maternal smoking, depressive symptoms, and alcohol use attenuated the associations between SES and child BPI by 26% to 49%. These maternal health conditions often occurred together, persisted over time, and were associated with the mother's own childhood SES and pre-pregnancy health. CONCLUSIONS: Social disparities in women's health conditions may help shape the likelihood of behavior problems in the subsequent generation. Improved public health programs and services for disadvantaged women across the lifecourse may not only address their own urgent health needs, but reduce social disparities in the health and well-being of their children.