This paper uses a search model of monetary exchange to provide new insights for evaluating the welfare costs of inflation. We first show that the search model of money can rationalize the estimates of the welfare cost of inflation based on the “welfare triangle” methodology of Bailey (1956) and Lucas (2000) provided that buyers appropriate the social marginal benefit of their real balances. For other mechanisms, the measure given by the welfare triangle has to be scaled up by a factor that increases with sellers' market power. We introduce capital and endogenous participation decisions and study how the cost of inflation is affected. We provide calibrated examples in which a deviation from the Friedman rule is optimal.