It is evident from previous research that user satisfaction is a multidimensional, subjective variable which can be affected by many factors other than performance of the system or searcher. This article draws on information retrieval and information systems literature in an attempt to understand what user satisfaction is, how it is measured, what factors affect it, and why findings on user satisfaction have been so varied and contradictory. It concludes with recommendations for future investigation of the use of user satisfaction as a measure of system performance. (Contains 1 table.)