Much has been written about service guarantees and their various proposed benefits. Following the literature, many writers regard a guarantee as a tool to jump-start quality improvements and/or see in them the ultimate way to gain a competitive edge. The objective of this paper is to consolidate our understanding of the working of guarantees. Based on a literature review and an exploratory study, a set of explicit propositions on the impacts of service guarantees was advanced. These propositions were then integrated into a single conceptual model. The model shows the impacts of well-designed guarantees on operations and service quality, consumer behavior, and finally on business performance.