This paper develops two models of the reference interview: (1) the Need-Oriented Model, which emphasizes identifying the client's information needs and allows for a broad-ranging diagnostic interview; and (2) the Question-Oriented Model, which is constrained by the client's initial question and focuses on refining that specific question, identifying why the client needs the information only if the client raises the issue. The models are then related to various environmental features of reference service such as the physical setup of reference service and staffing. Suggestions for promoting more involved interviews are offered. (MES)