Decentralization is one of the most dramatic political and economic trends in the last few decades. This book seeks to address its causes, exploring decentralizing reforms in Bolivia, Columbia, Ecuador, Peru, and Venezuela. It probes questions of where and why decentralization is adopted, what form it is likely to take in different contexts, and how it is likely to evolve over time. The book develops a theory linking decentralization's adoption to the electoral concerns of political parties: decentralization represents a desirable strategy for parties whose support at subnational levels appears more secure than their prospects in national elections.