Most demographic research on the effects of infant feeding and maternal nutrition on child spacing focused narrowly on the effects of one of these factors (usually breast- or mixed-feeding or maternal body weight at a point in time) on the birth hazard. Little insight into the relationships between these two sets of factors (infant feeding and maternal nutrition) or into a dynamic and complete analysis of the various effects of infant feeding and maternal nutrition has been provided. A comprehensive model will be developed which will (1) analyzed the separate and interactive effects of the full pattern of infant feeding on coital behavior, contraceptive behavior, maternal diet and nutritional status and time from birth to menses and menses to conception; (2) analyze the effects of maternal diet and nutritional status on these same outcomes; and (3) develop a simulation model to use our estimated model to examine the partial and total effects of changes in infant feeding and maternal nutrition on the endogenous variables of interest. This study utilizes a unique longitudinal data base designed to collect prospective data on over 2,600 Filipino mothers on a bimonthly basis from pregnancy through 24 months beyond delivery. The data, which were collected and computerized under separate funding, came from a survey designed specifically for this project. The data set will be one of the most exhaustive ever collected for examining these relationships. It will contain complete infant and maternal dietary and body composition (anthropometric) information and other proximate variables as well as an socioeconomic, cultural and related data. The analysis will be done by a multidisciplinary group which was involved in designing the data set and has worked together closely for several years on related research activities.