Two features of population planning are of special interest to operations researchers: the important interaction among family planning, health, and economic development, and the substantial but varying impact of social, cultural, political, and economic factors—features that require a multi-disciplinary, flexible approach for which operations research is well suited. In spite of the vast differences among various international settings, three overriding principles should be borne in mind. First, programs of population planning are designed to serve national goals, whereas the ultimate actions concerning family limitation are usually recognized to be private family decisions. Second, one usually faces a rather ill-defined interplay among a great variety of factors. Third, the universal importance of the population problem in developing countries is always coupled with severe limitations of resources to cope with the problem. This paper deals initially with the family decision process and then with the organization of professional activities toward population control. In both cases hypothetical models are developed, information from the field is used to illustrate their significance, and suggestions for further research are offered. The decision model considers the utility of child-bearing for different population groups compared with the subjective valuation these groups give to contraception. Means of measuring these poorly defined values are proposed. In assessing the role of operations research in the organization and delivery of family planning services, the paper directs attention to the allocation problem, which includes concern, on the one hand, for the methods of contraception provided, the manner in which they are offered, and the kinds of personnel employed, and, on the other hand, the attitudes of target populations toward both the services and the providers.