Subnational research (SNR) plays an increasingly prominent and important role in Comparative Politics. This article assesses the theoretical and methodological contributions of SNR. In particular it demonstrates the capacity of SNR to strengthen theory building by mitigating the problem of “theory stretching” and shows its comparative advantage for crafting multilevel theories that provide stronger explanations of outcomes of interest. With regard to methods and research design, the article offers new research strategies and shows how SNR can be combined fruitfully with a diverse set of widely-used methodologies.