Undertaken for a doctoral dissertation, this research project on reference services tested a model of major variables that influence academic library reference service outcomes. The study focused on reference librarians who serve in boundary spanning roles, i.e., positions where interchange with the organization's external environment is central to their function. It is argued that these roles are defined in part by the reciprocal roles of their clients, and that understanding the effectiveness of reference personnel requires the study of users as well. Based on these arguments, the model of the reference process that was developed for this study provided for the collection of information on individual reference transactions from both librarians and users. The model was tested through a study of 257 reference transactions from five academic libraries in northern California. The primary method of collecting data was through survey questionnaires for librarians and users. Data were summarized and analyzed by stepwise regression. It was found that variables related to feedback, service orientation, time constraints, and task uncertainty have the most significant effects on service outcomes. It was also found that for the majority of reference transactions, librarian judgments of service value are an adequate substitute for user service value judgments. (CGD)