Popular trust in political institutions is vital to democracy, but in post-Communist countries, popular distrust for institutions is widespread, and prospects for generating increased political trust are uncertain given disagreements over its origins. Cultural theories emphasizing exogenous determinants of trust compete with institutional theories emphasizing endogenous influences, and both can be further differentiated into micro and macro variants. Competing hypotheses drawn from these theories are tested using data from 10 post-Communist countries in Eastern and Central Europe and the former Soviet Union. Aggregate data on economic and political performance are combined with survey data on interpersonal and political trust, political socialization experiences, and individual evaluations of national performance. Results strongly support the superiority of institutional explanations of the origins of political trust, especially micro-level explanations, while providing little support for either micro-cultural or macro-cultural explanations. This encourages cautious optimism about the potential for nurturing popular trust in new democratic institutions.