Hospitalists are physicians who spend at least 25% of their professional time serving as the physicians-of-record for inpatients, during which time they accept "hand-offs" of hospitalized patients from primary care providers, returning the patients to their primary care providers at the time of hospital discharge. The hospitalist movement is only about 5 years old, yet at least 7000 hospitalists practice today and an estimated 19,000 will ultimately practice, approximately the current number of emergency medicine physicians. The emerging positivist literature on hospitalists' impact is the subject of this review. It traces the nature and evolution of the hospitalist movement; summarizes empirical evidence about costs, clinical outcomes, patient satisfaction, and education; and appraises whether the hospitalist model is indeed novel. The review concludes by outlining research questions about the hospitalist model's viability over time, the mechanisms by which it produces benefits, and especially hospitalists' longitudinal effect on continuity of patient care. A literature "scorecard" might rank evidence to date on costs as positive, evidence on clinical outcomes and education as nonnegative, and evidence on patient satisfaction and continuity of care as inconclusive. Above all, longitudinal research must illuminate whether hospitalists' advantages come at the cost of the doctor-patient relationship.