The purpose of this project is to develop and test models of social stratification that capitalize on the actual occupations that emerge around functional niches in the division of labor. To do so, the project will employ large-scale surveys from the United States and other countries. The trend in recent theoretical approaches has been to dismiss these phenomena as sociologically trivial. However, doing so ignores evidence that important social class processes occur principally at the subclass level. One virtue of disaggregating to this level is that the nominal categories of aggregate class analysis can be replaced by groupings which are meaningful not merely to sociologists but to the lay public as well. Disaggregation should yield new evidence on such basic issues as (a) the fluidity of modern mobility regimes, (b) the structure of recent trends in inheritance, persistence, and inter-occupational mobility, (c) the macro-level causes that generate immobility, and (d) the viability of convergence models in characterizing cross-national patterns of stratification. The proof of our approach thus rests on the additional explanatory power that accrues from referencing the real institutional processes by which classes are formed, mobility is constrained, and lifestyles are defined.