The history of medicine has come to occupy a significant place in our understanding of modern society and the American cultural fabric. To fully understand and appreciate American medicine in the twentieth century one must contend with the twin processes of specialization and professionalization. Grand Rounds considers the critical period for these two processes, the years between World War I and the Vietnam era. A diverse group of contributors (clinicians as well as historians and "participant-observers") outline broad themes involved in the evolution of modern internal medicine and trace the origins of sub­specialties such as cardiology, gastroenterology, rheumatology, infectious diseases, and nephrology. Paul Beeson, Rosemary Stevens, and others discuss the literature, diagnostic approaches, and therapeutic research in the field. Grand Rounds will be of interest to historians of science and medicine, students of American civilization, and medical practitioners.