The phenomenon of customer misbehavior, i.e. deviant, threatening or even violent customers, is not unusual and it causes problems for the firm, its employees, and other customers. Hitherto much research has focused on the hospitality industry (e.g. restaurants, hotels and bars) where misbehavior often is explained by service failures or customers’ characteristics. The purpose of this paper is to provide an enriched understanding of antecedents of misbehavior, by considering how the incidents are related to the structural design of the service. An interview study inspired by the critical incident technique, conducted with frontline employees that work onboard busses and trains, resulted in a rich empirical material. The employees reported a number of different types of incidents, ranging from offensive and insulting comments and fare dodging, to threats and even physical violence. The result showed, as could be expected, that some incidents were related to service failures. However, on several occasions, customer misbehavior was triggered by both features of service work and the service design, rather than by service failures. In fact, even managerial interventions to prevent misbehavior sometimes had the opposite effect. For example, procedures intended to create a safe environment generated minor as well as considerable customer misbehavior incidents.