The authors develop an overlapping-generations model of endogenous growth in which human capital is the engine of growth and the generations are linked through material and emotional interdependencies within the family. Parents invest in their children to achieve both old-age support (care) and emotional gratification, and material support from children is determined through self-enforcing implicit contracts. The authors show that optimal intergenerational trade can then lead to maximization of growth opportunities. Their model produces a theory of the "demographic transition" linking longevity, fertility, and economic growth. Copyright 1991 by University of Chicago Press.