The World Federation for Medical Education (WFME) curricular standard #2 is that medical schools must throughout the curriculum teach the scientific method. In problem-based learning (PBL) Howard Barrows has written that hypothetico-deduction is the scientific method of clinicians. We discuss how the scientific method can be used daily in PBL. The Group of Related Diseases Display (GRDD), as an educational scaffold used by some PBL students, is introduced. The GRDD facilitates the forward clinical reasoning exercise (CRE) in which the tutor plays a simulated patient, and the reverse CRE, in which students write a new case and simulate the patient. In a pilot study, students from Kyungpook National University, Daegu, Korea had high regard for reverse-CRE. PBL may be ready for the next developmental stage, in which Bloom's higher levels of educational goals - that of knowledge application (forward CRE) and knowledge synthesis (reverse CRE) are explored.