The hospitalist movement mirrors the health care trend toward ever-increasing specialization. However, hospitalists are fundamentally generalist physicians who provide and coordinate inpatient care, often aided by myriad subspecialists. How can a generalist be a specialist? Specialties in medicine are traditionally defined by organ (eg, cardiology), disease (oncology), population (pediatrics), or procedure/technology (surgery or radiology). The hospitalist, on the other hand, is a "site-defined generalist specialist" (similar to emergency medicine physicians or critical care specialists), caring for patients with a wide array of organ derangements, illnesses, and ages within a specific location.45 Accordingly, the hospitalist should not be seen as a retreat from generalism and its emphasis on coordination and integration9,77 but rather as an affirmation of these values and as a surrogate for the primary care physician in the hospital. The competing pressures resulting from the distance between office and hospital as well as the requirement of around-the-clock availability make the hospital-based generalist a logical evolution. Hospital medicine has already satisfied many of the requirements of a specialty. A large and enthusiastic group of practitioners identify themselves not according to their training background but as hospitalists. The NAIP is almost certainly the fastest growing physician society in the United States. The field hosts several successful meetings each year and has its own clinical textbook.78 To establish themselves as members of a recognized medical specialty, hospitalists must identify a core skill set or body of knowledge and obtain the approval of credentialing organizations. Advocates of specialty status for hospitalists should be encouraged by the history of 2 other site-defined inpatient specialties: emergency medicine and critical care medicine. Like these relatively young fields, it seems probable that hospitalists will ultimately define a unique set of skills and competencies that will distinguish their field. The identification of practice-training mismatches (Table 2) represents an important first step. Credentialing organizations deliver the final stamp of approval on new specialties by creating a board certification or added qualification. Most new fields quickly agitate for such status, their motivation both practical and visceral. However, for unique reasons, few hospitalists are pressing this point. Many physicians—hospitalists and nonhospitalists—worry that if a credentialing body (such as the American Boards of Internal Medicine or Pediatrics) created a hospital medicine credential, health maintenance organizations might require that physicians possess this credential to care for inpatients. This would be unacceptable to many primary care physicians, who would be excluded from the hospital despite their desire and competence to continue practicing there. For this reason, we expect neither NAIP nor the relevant boards to promote separate credentials in the near future. Nevertheless, as evolutionary forces lead to specialized training, some formal specialty designation may emerge.79