Loyalty programs (LPs) have increased in popularity, and have been studied extensively in the academic literature with mixed findings. Therefore, we offer an overview of extant research on LPs. We derive generalizations on the effectiveness and best design of LPs, discuss conditions that mediate and moderate the effects of LPs on customer behavior and attitudes, and highlight avenues for further research. Overall, we conclude that LPs are effective in increasing consumer purchase behaviors over time, but their impact differs across consumer segments and markets. Numerous practical examples illustrate the points discussed. Overall, this monograph provides insights to researchers and practitioners through a comprehensive, research-based synthesis of current knowledge. As a consequence, LP managers may better understand the implications of LP adoption, and ultimately improve the effectiveness of their LPs.