After three decades of research on the demographic significance of family planning programs, a consensus is emerging that these programs can constitute a fertility determinant. This volume presents an overview of the research evidence on the demographic role of family planning programs. Chapters address this subject from perspectives that are prominent in the economic and sociological literatures on the nature of contraception, and how that demand relates to such program functions as normative change, legitimation of birth control, education, and supply of services. The authors challenge the assumption implicit in much of the literature, that demand- and supply-side determinants are conceptually distinct: the two can interact, each stimulating growth in the other. Methodological and theoretical issues in efforts to measure program effects on fertility are reviewed, and the practical utility of theory in the design of sociologically appropriate family planning programs is appraised.