Purpose: The paper explores negative customer interactions in retail from a front line employee perspective. It particularly focuses on how such incidents are defined and perceived against a backdrop of service work. Methodology: The paper draws on 35 in-depth interviews with front line staff in three retail industries (groceries, consumer electronics and women’s fashion) where the respondents report on their experiences with customers who they perceive as troublesome in one way or another. Episodes of customer misbehaviour were identified and analysed using the critical incident technique and the NVivo software for qualitative data analysis. Findings: Several generic forms of customer misbehaviour were identified both within and across the industries, and are illustrated in the paper. While congruent with previous research on customer misbehaviour on an overall level, a closer analysis of what the respondents perceived as “deviant” reveals an interesting aspect of service work in modern retailing. Whereas customers’ interactional shortcomings (e.g. rudeness and unsociability) were partly seen as natural (albeit not fully accepted) aspects of service work, the tolerance for behaviour that infringed on operational efficiency were much more limited. Arguably, this indicates that efficiency is more profound to retail services than is generally acknowledged. Originality: Traditionally, service management has been firmly rooted in a win-win paradigm, where company interactions with customers are supposed to be constructive, harmonic and mutually value creating. However, this ideal is not always lived up to in service practice. While much has been said about interactional failures as perceived from the customers’ side, research taking an employee perspective is still spares. As the present paper show, such a perspective adds valuable knowledge not only about service work but also about the service itself.