A major factor that contributes to the high rates of medical error in the treatment of patients with diabetes and other chronic diseases is the complexity of the tasks that physicians must complete. SimCare is a model of the clinical care setting for patients with type 2 diabetes. The model was designed to support investigation of physician cognition and decisionmaking activity. SimCare is dynamic and interactive and simulates diabetes management in the office-practice setting. SimCare presents a series of cases based on clinical situations representing task features that are thought to be the source of both realistic care decisions and medical errors. Once a simulated clinical case is initiated, physicians select treatment options (termed "moves") from an unguided set of choices similar to those available in routine office practice. The cumulative record of the chosen treatment moves is available for analysis and comparison with an expert's sequence of moves for each simulated patient. SimCare is potentially both an assessment and a teaching tool that enables the observation and analysis of decisionmaking in the simulated practice setting. This paper discusses the use of this tool to identify potential sources of medical errors and guide customized learning interventions designed to reduce them.