The Internist, called general physician in some countries, is a physician who specializes in the prevention, diagnosis and medical treatment of diseases of adults. Internists are skilled in the management of patients with undifferentiated or multi-system disease and care for patients in hospital, out patient clinics or ambulatory settings.

Internists may have subspeciality interests in diseases affecting particular organs or systems and subspecialities of internal medicine include allergy and immunology, cardiology, dermatology, endocrinology, haematology, infectious diseases, gastroenterology, nephrology, neurology, oncology, pulmonology, and rheumatology. Geriatrics is a subspeciality concerned with the care of the elderly. Some internists work as hospitalists managing hospital in patients only.