In outpatient surgery, also called ambulatory or same-day surgery, patients normally require hospital care for less than 24 hours. These operations are increasingly being used because advances in surgical technology and anaesthesia enable surgeons to perform many operations formally limited to inpatient care.

The federal agency's analysis of data available from 28 states found that in 2007:

This AHRQ News and Numbers is based on data in Hospital-Based Ambulatory Surgery, 2007. The report uses statistics from 28 States that provide data to the Healthcare Cost and Utilization Project State Ambulatory Surgery Databases and their corresponding State Inpatient Databases. These databases provide information on hospital-based ambulatory and inpatient surgeries performed in short-term, acute care hospitals.; Source: Agency for Healthcare Research and Quality (AHRQ)