In Apri1 1973 the National Center for Health Statistics inaugurated the National Ambulatory Medical Care Survey to gather and disseminate statistical information about ambulatory health care provided by office-based physicians to the population of the United States. It is the purpose of the present report to relate the current survey design characteristics and to describe the background and methodology for developing the National Ambulatory Medical Care Survey. SeIected feasibility study findings are presented to illustrate collected data and suggest kinds of information that may be expected when substantiate survey results become available on a continuing national basis.