As our knowledge of human biology becomes more complex and the medical school applicant pool declines, there is ample reason to consider an alternative to the conventional medical curriculum. Many authorities feel that a format incorporating problem-based learning (PBL) would be more appropriate and effective. The problem-based medical curriculum is one in which facts and principles are learned in the context of a clinical problem. Problem-based medical education began as a revision of the McMaster University medical curriculum in 1969 and was instituted in the United States as a problem-based experimental track at the University of New Mexico School of Medicine in 1979. The first completely integrated, totally problem-based, McMaster-type, medical curriculum in the United States began operation in 1982 with the establishment of Mercer University School of Medicine. Many years of experience at these three institutions have shown that the problem-based curriculum works well. Several medical schools throughout the world are either practicing PBL or investigating the feasibility of adopting it. A comparison of the costs (in faculty time) of problem-based and conventional pathology programs suggests that the PBL curriculum is quite feasible for schools with a class size of 60 or less and may be so for many schools and programs with classes of less than 100.