Consumers in many countries often give voluntary payments of money (tips) to the workers who have served them. These tips are supposed to be a reward for service and research indicates that they do increase with customers’ perceptions of service quality. This paper contributes to the service-tipping literature by examining numerous potential moderators of this relationship in two studies. Results indicate that the service-tipping relationship is robust across meal type, day of week, sex and race of server as well as customers’ alcohol consumption, education, income, race, worship frequency, and hospitality work experience, but that it is stronger for older consumers than for younger ones and for parties with large bills than for parties with smaller bills. The practical and theoretical implications of these and other findings are discussed.