This review article assesses the accomplishments and limitations of the best of recent research on democratization and democracy in Europe, South America, and post-Soviet Eurasia with regard to the challenge of theory building. Concerning the dependent variables of this literature, the article argues that the concepts of democratic transition, democratic consolidation, and democratic quality, as currently conceptualized, do not provide a clear focus for causal theorizing. It recommends, rather, that the proper subject matter of regime analysis should be the origins and stability of regime types and suggests how the semantic field of democracy studies could be clarified through a focus on the concepts of democratic transition and democratic stability. Relatedly, it argues that democracy scholars have made unwarranted use of aggregate and dichotomous measures and advocates instead the use of more disaggregate and nuanced measures. Concerning causal theories, the article shows that researchers have identified a range of potential explanatory factors and proposed suggestive complex causal models. Nonetheless, it also argues that democracy scholars have rarely formulated clearly specified general causal models and identifies some key pitfalls to be avoided as scholars tackle two key tasks: the development of thick and general theory and the definition of causal models. The conclusion raises the need to place theory building in context and argues that scholars must also turn their attention to the demanding challenges of data generation and causal assessment.