Two explanations for the effects of alcohol on prosocial behavior—that is, mood enhancement and cognitive impairment—suggest that restaurant diners should tip more when they have consumed alcohol than when they have not. However, previous attempts to find a relationship between percent tip and alcohol consumption have failed. This failure may be due to statistical problems associated with using percent tip as a measure of tipping. This article reports a study that uses as a dependent variable residuals from a regression of bill size on tip amount. The results of this study indicate that alcohol consumption is positively related to tipping.