A number of macro-economic-demographic models have been created for developing countries during the decades of the 1970s and 1980s. Such models purport to simulate relationships between demographic variables and the process of socioeconomic development in the particular country, with the dual purposes of enhancing our knowledge of the process in particular settings and, by examining alternative scenarios, providing useful information to policy makers on the selection of demographic and economic policies to enhance economic development and improve human welfare. This paper 1st reviews the antecedents and then focuses on assessing the demographic functions (fertility, mortality, and internal migration rates) used in the 2 families of models which have had perhaps the largest number of applications in developing countries--the Bachue models, originating at the International Labour Office (Geneva), and the ESCAP models, originating at the Economic and Social Commission for Asia and the Pacific (Bangkok). Each has been applied, with significant variations, in at least 3 countries. Economic-demographic functions are defined as endogenous (and substantively meaningful, from the points of view of this paper) whenever there is an effect of economic growth or change in economic structure on the particular demographic function. The bulk of this paper assesses the realism and endogeneity of the fertility, mortality, and migration functions used in the Bachue and ESCAP models, noting, where possible, both the apparent and prima facie behavioral relationships and those that are actually important on the dynamic simulation. Shortcomings are described, including the lack of government expenditure functions with effects on demographic variables. The paper concludes more positively, noting areas of congruence and appealing endogenous relationships and functional forms specified in certain country models. It also suggests further development of, on the 1 hand, both simpler and more realistic planning models (focusing on particular behavioral relationships or sectors of importance to the country), which will be easier for country planners to understand and hence use, and, on the other hand, more complex research models aimed at enhancing our understanding of fundamental, dynamic relationships between economic factors, government policies and fertility, mortality and migration rates during the course of socioeconomic change.