This article describes part of a project designed to develop a user-based approach to measuring the quality of an information service, that is, the extent to which the service provided by the library meets or exceeds the users' expectations for an excellent or superior service on a consistent basis. The main question investigated is whether there are differences in the expectations that academics hold of information services provided by academic libraries, and librarians' perceptions of these expectations. The results show that academics and librarians have similar expectations but there are differences in the emphasis each group places on aspects of service. Librarians, for example, underestimate the importance to academics of the responsiveness of a service and overestimate the importance of the characteristics of the staff who provide the service. Practical applications of the findings are discussed and theoretical implications explored.