Medical school teachers must have an accurate idea of the doctor's clinical reasoning process (CRP) in order to provide students with learning experiences and evaluations that will ensure their acquisition of an effective and efficient CRP. It is difficult to derive this understanding from much that has been written on the subject. It is important to recognize that clinical problems are ill-structured and that the doctor's reasoning is built around a temporal unfolding of information. A model for the CRP is described along with a critique of other models that have been suggested. The results of research that examines components of the process must be seen in relation to the overall process.