Ambulatory surgery is arguably among the most important trends affecting healthcare in the last quarter of the twentieth century. Indeed, more than half of surgery done in the United States moved out of the hospital during the past 20 years. Ambulatory surgery accounted for an estimated 66% of surgery done in the United States in 1995 and is expected to reach 73% by the year 2000 (personal communication, John A. Henderson, SMG Marketing Group, Inc, August 1995). Clearly, this shift in the locus of surgery could not have occurred unless patient outcomes following ambulatory surgical care were at least comparable to those associated with inpatient care. Critically important in fostering this transition has been anesthesia care tailored to surgery in the ambulatory setting. Reviewing the way ambulatory anesthesia has developed not only helps to understand the current status of this rapidly growing anesthesiology subspecialty, but also how the field is likely to evolve in the coming years.