We are currently completing a study of the cognitive processes involved in problem-solving tasks that arise in transfusion services laboratories. This study has included a series of empirical studies of both medical technology students and practitioners in order to identify cognitive errors and inefficiencies associated with such problem-solving tasks and to provide the basis for developing cognitive models of expert and less-than-expert performances. These studies raise serious questions about current education and practice. We have found that there is little agreement among laboratories on procedures for such basic tasks as antibody identification. (Indeed some laboratories have no standard protocols at all for such tasks.) We have also found very significant differences among practitioners in terms of their levels of expertise. Finally, we have found that even highly expert practitioners make slips during problem solving. We therefore propose a combination study which will build upon these results to develop a tool kit to: 1. Support problem-solving activities in the laboratory in order to reduce errors and improve efficiency; 2. Provide embedded training to increase the expertise of practitioners while on the job. This tool kit will provide a set of cognitive tools that the practitioner can access, and will be an enhancement of a functional tutoring system, (the Transfusion Medicine Tutor) that we have already developed. The final product will be a prototype tool kit which has been extensively evaluated, as well as documentation of our design process (which can serve as a model for developing other medical support systems).