This thesis investigates customer-to-customer roles and impacts in the context of service encounters. This topic is studied from two angles: customer interactions during group service encounters and customer perceptions post service encounters. The first angle is a focus on group service encounters that addresses the lack of research on customer-to-customer interactions that occur in customer-to-customer interaction-intensive contexts. These are contexts where the interactions between customers are not peripheral to the service, where there can be an expectation to interact with the other customers, and are common in tourism and hospitality, recreation, and education. The second angle is a focus on service outcomes after the service encounter, including satisfaction, intention to recommend, and online word-of-mouth. Paper 1 explores how firms view and manage customer-to-customer interactions during group service encounters. It finds that the differences in attitude and conduct of firms create four possible stances toward customer-to-customer interaction. Paper 2 delves deeper into how customer-to-customer interactions impact the design and delivery of group service encounters, develops a typology of customer cohort climates (CCCs), and identifies how each CCC can be created through four elements of group service encounters. Paper 3  investigates how positive and negative customer-to-customer interactions impact service outcomes and finds that customer-to-customer interaction is a dissatisfier. Paper 4 examines how customers produce online hotel reviews and finds that content analysis of online reviews yields similar findings to more traditional quantitative research methods. This thesis advances research on the impact of customers on each other and provides evidence that other customers can and should be managed to achieve desired service outcomes. It further proposes how these interactions can be managed to further enhance service firm offerings. / <p>QC 20160516</p>