Synthetic research in comparative/historical sociology involves the integration of internal analysis (within country inference) and external analysis (between country inference). This process is explained through a model of the comparative research process that focuses on the differences between internal and external analysis. After presenting the range of possible synthetic research strategies, the problems involved in four empirical works that attempt synthetic strategies are discussed. The paper concludes that studies combining time series with history seem most likely to achieve synthesis, especially when those quantitative studies include some variables specific to each country (maximal models) rather than repeating the same rigid models for all countries (comparative models). Completely synthetic studies with large Ns are, however, much less likely to be done.