The 3-year medical school program at McMaster University encourages an approach to learning a physician can apply throughout his or her career. The program has four phases and provides early exposure to relevant clinical material. In phase 3, the basic science phase, the structure and function of organ systems in health and disease are studied. Understanding the mechanisms of disease in order to be able to relate clinical symptoms and signs to physiologic and pathologic processes is emphasized. The four 10-week units deal with groups of organ systems. The "blood and guts" unit teaches the student hematology and gastroenterology through a variety of problem-based methods. Specialists in the relevant scientific disciplines influence selection and construction of the problems presented. The students are evaluated by the faculty tutor on their accomplishment of specific objectives related to their competence in solving biomedical problems.