Inpatient hospital services constitute the largest share (29%) of total national health care spending. Hospitalizations for children cost $37 billion annually. The traditional model, in which inpatient care has been provided by primary care pediatricians is being replaced by a new model of pediatric hospitalists whose primary or exclusive professional focus is the care of hospitalized patients. This shift has been driven by the increasing illness severity and complexity of hospitalized children, the challenges in managing these children by office-based pediatricians, and the increasing demand for higher quality, and more efficient and cost-effective hospital care.