The recent trend toward problem-based learning (PBL) in American medical education amounts to one of the most significant changes since the Flexner report motivated global university affiliation. In PBL, fundamental knowledge is mastered by the solving of problems, so basic information is learned in the same context in which it will be used. Also, the PBL curriculum employs student initiative as a driving force and supports a system of student-faculty interaction in which the student assumes primary responsibility for the process. The first PBL medical curriculum in North America was established at McMaster University in Toronto in 1969. The University of New Mexico was the first to adopt a medical PBL curriculum in the United States, and Mercer University School of Medicine in Georgia was the first U.S. medical school to employ PBL as its only curricular offering. Many interpretations of the basic PBL plan are in use in North American medical schools. Common features include small-group discussions of biomedical problems, a faculty role as facilitator, and the student's relative independence from scheduled lectures. The advantages of PBL are perceived as far outweighing its disadvantages, and the authors conclude that eventually it will see wider use at all levels of education.