We conducted a meta–analysis of Rusbult's Investment Model of commitment. Across 52 studies, including 60 independent samples and 11,582 participants, satisfaction with, alternatives to, and investments in a relationship each correlated significantly with commitment to that relationship. Moreover, these three variables collectively accounted for nearly two–thirds of the variance in commitment. Commitment, in turn, was found to be a significant predictor of relationship breakup. Support for the model was obtained in predicting commitment in both relational domains (e.g., commitment to a romantic partnership) and nonrelational domains (e.g., commitment to one's job), but was significantly stronger in relational domains. Additional moderator analyses suggested that the associations between commitment and its theorized bases vary minimally as a function of demographic (e.g., ethnicity) or relational (e.g., duration) factors. We review theoretical strengths and shortcomings of the Investment Model and identify directions for future research.