Economic forces have stimulated a growing role for physician "hospitalists" in caring for patients hospitalized by other physicians, and the question of whether hospital care constitutes a new medical specialty has been raised. Three recently recognized specialties--emergency medicine, family practice, and critical care--originated from trends in medical practice. All three fulfill the major criteria for a medical specialty: scientific legitimacy, the development of new training pathways, and the existence of academic departments. The hospitalist movement is currently underdeveloped in each of these areas. By training, most hospitalists are internists who are well prepared to care for inpatients. Internal medicine must determine how this new movement fits into the traditional framework of general internal medicine and medical subspecialties. Until it does, the future of inpatient medicine as a recognized specialty will remain uncertain.