Licensed freestanding facility, other than a physician’s office, at which outpatient medical services are provided on an ambulatory basis (e.g., diagnosis, treatment, same-day surgery, rehabilitation). ASCs are hospital based (or sponsored) or independently owned (or sponsored). Surgery of an uncomplicated nature that traditionally was done on an inpatient basis but can be performed with equal efficiency without hospital admission is now being done in an ASC. To receive payment for Medicare patients, the facility must have an agreement with the Centers for Medicare and Medicaid Services (CMS) and meet specific requirements. ASCs are paid according to nine different payment groups based only on their cost similarities. Also called surgicenter or ambulatory surgical center.