Customer gratitude represents the emotional core of reciprocity and plays a key force in developing and maintaining successful seller–buyer relational exchanges. Based upon personal interviews with 239 members of loyalty card programs of a department chain store, this study shows that alternative relationship marketing investments (i.e., direct mail, tangible rewards, interpersonal communication, and preferential treatment) have a differential influence on customers' gratitude and consequently behavioral loyalty. More specifically, results of this study indicate that preferential treatment is the most effective relationship marketing tactic to enhance customer gratitude, followed by interpersonal communication and tangible rewards, respectively. Management implications for retailers to increase customers' gratitude are discussed.