Among schools of thought in comparative research, Rational Choice Theory (rct) is both the most systematic and the most contested. rct lacks a “classical” foundation but offers a clear internal theory structure. The rationality assumption contains an unquestioned heuristic aspect, although the determinants of choice (especially preferences) lack a universally accepted solution. The choice aspect addresses the understanding of social phenomena as the result of individual actions seen in light of the possible alternatives. This view unifies scholars in the Rational Choice tradition and leads to the macro-micro-macro-scheme. Micro-oriented comparative research has flourished through the availability of multi-level data sets in fields such as social capital theory, social stratification and mobility, including educational attainment or the inclusion of migrants, family studies, criminology, and labor markets. Institutional rct-based comparative research has addressed welfare states, religion, and general questions. In both aspects, rct leaves room for further productivity in comparative research.