Subnational units of analysis play an increasingly important role in comparative politics. Although many recent studies of topics such as ethnic conflict, economic policy reform, and democratization rely on comparisons across subnational political units, insufficient attention has been devoted to the methodological issues that arise in the comparative analysis of these units. To help fill this gap, this article explores how subnational comparisons can expand and strengthen the methodological repertoire available to social science researchers. First, because a focus on subnational units is an important tool for increasing the number of observations and for making controlled comparisons, it helps mitigate some of the characteristic limitations of a small-N research design. Second, a focus on subnational units strengthens the capacity of comparativists to accurately code cases and thus make valid causal inferences. Finally, subnational comparisons better equip researchers to handle the spatially uneven nature of major processes of political and economic transformation.