The debate about the relative merits of presidentialism and parliamentarism has a long history, but it was revived in 1990 with Juan Linz's articles about the supposed perils of presidentialism and the virtues of parliamentarism. The argument presented in this review is that we are now witnessing a 'third wave' of presidential/parliamentary studies since 1990. The 'first wave' began with Linz's articles. It was characterized by a debate in which there was one explanatory variable (the regime type) and one dependent variable (the success of democratic consolidation). The 'second wave' of presidential/parliamentary studies began around 1992-93. In the 'second wave' there is more than one explanatory variable (the regime type, usually, plus the party system and/or leadership powers) and often a different dependent variable ('good governance' as opposed to democratic consolidation). The 'third wave' is quite different. This work is informed by more general theories of political science. Here, the respective merits of presidential and parliamentary regimes are not necessarily the sole focus of the work. However, its overarching approach informs the debate in this area in a more or less direct manner. The argument in this review article is that the 'third wave' of studies has much to offer the ongoing debate about the relative merits of presidentialism and parliamentarism.