This chapter compares the role that constitutions play in democracies with the role they play in autocracies. To be able to differentiate these roles, various attempts to delineate autocracy from democracy are discussed. To assess the performance of autocratic countries, it is proposed to distinguish different types of autocracies. The chapter also discusses the determinants that make countries either democratic or autocratic. Finally, the most relevant theories inquiring into the determinants of regime change – i.e., a change from autocracy to democracy or the inverse – are discussed and confronted with empirical evidence.