The Council on Scientific Affairs of the California Medical Association presents the following epitomes of progress in pathology. Each item, in the judgment of a panel of knowledgeable physicians, has recently become reasonablyfirmly es-tablished, as to both scientific fact and clinical importance. The items are presented in simple epitome, and an authorita-tive reference, both to the item itself and to the subject as a whole, is generally givenfor those who may be unfamiliar with a particular item. The purpose is to assist busypractitioners, students, researchers, and scholars to stay abreast of progress in medicine, whether in their own field ofspecial interest or another. The epitomes included here were selected by the Advisory Panel to the Section on Pathology of the California Medical Association, and the summaries were prepared under the direction of Yutaka Kikkawa, MD, and the panel.