physician assistant (PA), health-care professional who provides patient services ranging from taking medical histories and doing physical examinations to performing minor surgical procedures; often called physician's assistant. Physician assistants work under the supervision of a physician, who can be on or off site. PAs receive two years of postgraduate training and pass a national certifying exam. They are licensed by the states. PAs, who typically deliver quality routine health care less expensively than doctors, are an increasingly important part of the American health-care system, as they are in Canada and some European countries.