This proposal presents a program of research to examine Nonmarital Fertility Patterns in the U.S. and ten selected Western nations. We propose to describe non-marital fertility patterns in the U.S. and its metropolitan areas in 1970 and 1980 and to examine its trends over time (since 1917) in the nation as a whole. We intend also to describe the trends and fluctuations in nonmarital fertility in ten Western countries from about 1947 to the present. Having described trends and patterns of nonmarital fertility, we propose next to attempt to estimate the determinants of its variation. Explanations of annual fluctuations in nonmarital fertility in the U.S. since 1940, and of cross-sectional patterns in nonmarital fertility among the states and metropolitan areas of the U.S. in 1970 and in 1980 will be guided by a socio-demographic theoretical model. This model derives from the classic work of Davis and Blake and is developed in detail in the proposal. Finally, we propose to describe the characteristics of U.S. women with nonmaritally conceived births, drawing upon data from the 1976 and 1982 National Surveys of Family Growth, and the six June Current Population Surveys for 1978 through 1983; we will also endeavor to estimate the degree of relationship between selected characteristics and the occurrence of non-marital fertility, using log-linear approaches, for the time periods between 1976 and 1983, again drawing on data from the above sources. The research proposed herein should provide detailed, theoretically-based, complete and statistically-precise information on macro- and micro-level patterns and explanations of nonmarital fertility.