This chapter introduces presidential government and contrasts it with parliamentary government. Several differences between the two are highlighted, with particular attention paid to the difficulty of making comprehensive policy in a presidential system, the nature of recruitment in the two systems, and the combining of the head of state and the political executive in a presidential system. The chapter addresses the question of why all democracies aren't parliamentary systems. The presidential system is presented as a way to overcome problems of instability but it, in turn, embraces fragmentation.