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We present a meta-analytic review of the literature on sex differences in the trust game (174 effect sizes) and the related gift-exchange game (35 effect sizes). Based on parental investment theory and social role theory we expected men to be more trusting and women to be more trustworthy. Indeed, men were more trusting in the trust game (g = 0.22), yet we found no significant sex difference in trust in the gift-exchange game (g = 0.15). Regarding trustworthiness, we found no significant sex difference in the trust game (g = −0.04), and we found men, not women, to be more trustworthy in the gift-exchange game (g = 0.33). These results suggest that men send more money than women do when their money is going to be multiplied, thereby creating an efficiency gain. This so-called “male multiplier effect” may be explained by a stronger psychological tendency in men to acquire resources.