Cumulating evidence exists that children of mothers with cognitive deficits are at risk for developmental delay, psychosocial mental retardation, and behavior disorders. The authors review the literature on the effects of genetic and environmental contributions to children's intellectual functioning and on the effects of preventive intervention designed to improve intellectual outcomes for high-risk children. Case studies from a longitudinal study of socioeconomically disadvantaged families are used to illustrate how low cognitive functioning affects maternal caregiving and how carefully planned interventions can enhance a mother's ability to provide a supportive learning environment for her young child. Key words: early intervention, environmental risk, maternal cognitive deficits