Although the acute hospital is the standard venue for treating acute serious illness, it is often a difficult environment for older adults who are highly susceptible to functional decline and other iatrogenic consequences of hospital care. Hospital care is also expensive. Providing acute hospital-level care at home, in lieu of usual institutional care, is viable. As an emerging service model, the definition of hospital at home (HaH) remains unsettled. Data favor HaH models that provide substantial physician inputs and are geared toward substituting for hospital care, provide service that is highly satisfying to patients and their caregivers, are associated with less iatrogenic complications, and are less expensive. Dissemination of HaH in integrated delivery systems is feasible. Widespread dissemination of HaH in the United States will require payment reform that acknowledges the role of HaH in the health care system.