A persistent puzzle in the social and biological sciences is the existence of prosocial behav- ior, actions that benefit others, often at a cost to oneself. Recent theoretical models and empirical studies of indirect reciprocity show that actors behave prosocially in order to develop an altruistic reputation and receive future benefits from third parties. Accordingly, individuals should stop investing in reputations via prosocial behavior when a future bene- fit (via indirect reciprocity) is unlikely. The conclusion that the absence of reputational incentives necessarily leads to egoistic behavior contrasts sharply with models of heteroge- neous social preferences. Such models demonstrate the theoretical plausibility of popula- tions composed of egoists and altruists. Results of Study One show that actors classified a priori as egoists respond strategically to reputational incentives, whereas those classified a priori as altruists are less affected by these incentives. Egoists act prosocially when reputa- tional incentives are at stake but not when opportunities for indirect reciprocity are absent, while altruists tend to act prosocially regardless of whether reputational incentives are pre- sent. These results suggest that altruistic behavior can result from non-strategic altruism or reputation-building egoism. Study Two replicates these results and explores indirect recip- rocation of others' prosocial acts. We found that altruists indirectly reciprocate at higher levels than egoists, and individuals tend to discount others' prosocial behaviors when they occur in the presence of reputational incentives. As a result, public prosocial behaviors are indirectly reciprocated less than private prosocial behaviors. In line with our argument that altruists pay less attention to reputational incentives, egoists showed a greater tendency than altruists to discount others' public prosocial behaviors. The results support the grow- ing focus on heterogeneity of individuals' social preferences in models of altruism and indi- rect reciprocity.