Physician (e.g., family practitioner, general practitioner, pediatrician, obstetrician/gynecologist, general internist) who sees patients first for most health problems, who oversees the care of patients in a managed health care plan (HMO or PPO), and who refers patients to specialists (e.g., cardiologist, oncologists, surgeons) for services as needed. Also known as a gatekeeper, primary care doctor, or primary care practitioner.