Restaurant tips are supposed to be an incentive/reward for the delivery of good service. In order for tipping to serve this function, consumers must leave larger tips in response to better service. Numerous studies have found a relationship between evaluations of service and tip size, but these studies have involved between-subjects, correlational designs that mean the observed relationships could be due to extraversion, friendliness, generosity or other stable dispositional differences between tippers that affect both service ratings and tip sizes. The current study attempts to rule out these alternative explanations by examining the tipping behavior of 51 people across multiple dining occasions. Results indicate that tip sizes are reliably correlated with service ratings after controlling for the identity of the tipper and, therefore, all potential stable dispositional difference confounds. The theoretical and practical implications of this finding are discussed.