This article discusses the importance of measuring how students perceive quality of service in online higher education. The article also reviews the existing literature on measuring users' perceptions about quality in e-services. Even when there are a lot of articles on this matter, none of them focuses on e-learning services, so this paper tries to fill that gap. The article proposes using the Critical Incident Technique to perform a qualitative analysis, which contributes to identify the main dimensions and categories that contribute to students' perception of service quality. A case study, regarding a completely online university, is presented and the proposed model is used to obtain some preliminary research results. Among these, key quality dimensions from a student point of view are identified. Some of these dimensions are: learning process, administrative processes, teaching materials and resources, etc. After discussing the research results, a list of recommendations for university managers is formulated. We believe that both the proposed methodology and the case-study recommendations can be of potential interest for managers of several universities offering online higher-education worldwide. (Contains 1 table and 4 figures.)