In the United States, Physician Assistants (PAs) are non-physician clinicians licensed to practice medicine with the supervision of a licensed physician. Unlike nurse practitioners, who are trained in advanced nursing, PAs receive education specifically in the practice of medicine.

In many states, PAs are licensed and work under the auspices of the physician's license. Physician Assistants generally have a master's degree in medicine from an accredited university. Practicing PAs require national certification (PA-C), which must be maintained by recertifying every two years by requiring at least 100 hours of Continuing Medical Education (CME) and taking a national recertifying exam every six years.

The physician supervision, in most cases, need not be direct, or on site, and many PAs practice in remote or underserved areas in satellite clinics. All states, as well as the District of Columbia, Guam, the United States Virgin Islands, and the Commonwealth of the Northern Mariana Islands have laws and/or regulations authorizing physician assistants to practice medicine. PAs can prescribe medications in all 50 states as well as D.C., Guam, and the U.S. Virgin Islands. PAs are assigned a DEA number that gives them authority to prescribe controlled medications in their scope of practice. They have specialized registration category assigned to "mid-level" practitioners.

PAs in surgical practices also serve as first assistants in surgery. PAs provide medical services that are reimbursed under Medicare and third party insurances. Their scope of practice and autonomy are only limited by their precepting physicians' scope of practice, comfort level, and the PA's clinical experience, allowing PAs to work in any area of medicine, surgery, or research.