The National Hospital Ambulatory Medical Care Survey (NHAMCS) was inaugurated in 1992 to fill a gap in data about ambulatory medical care in the United States. Although the National Ambulatory Medical Care Survey (NAMCS) collects annual data on patient visits to physician offices, it excludes the hospital emergency room and outpatient department visits that make up a large part of the total ambulatory care received each year. The NHAMCS provides data from samples of patient records selected from emergency departments (EDs) and outpatient departments (OPDs) of a national sample of hospitals. The resulting national estimates describe the use of hospital ambulatory medical care services in the United States. For the 1996 survey, data were collected from 235 OPDs and 392 EDs. Among the variables included are age, race, and sex of the patient, reason for the visit, physician's diagnoses, cause of injury (ED only), surgical procedures (OPD only), medication therapy, and expected source of payment ... Cf. : http://webapp.icpsr.umich.edu/cocoon/ICPSR-STUDY/02365.xml.