National Archive of Computerized Data on Aging

National Ambulatory Medical Care Survey, 1991 (ICPSR 6430)

Principal Investigator(s):


The National Ambulatory Medical Care Survey (NAMCS) provides data from samples of patient records selected from a national sample of office-based physicians. These national estimates describe the utilization of ambulatory medical care services in the United States. In 1991, there were 33,795 patient records provided by 1,354 doctors who participated in the survey. The survey obtains information on the age, race, and sex of the patient, and on physician characteristics such as geographic location and specialization. Data describing the nature of the office visit include the expected source of payment, patient's problem, prior visit status, referral status, physician's diagnoses, diagnostic and therapeutic services provided, and disposition and duration of the visit. Other variables cover drugs/medications ordered, administered, or provided during office visits, such as medication code, generic name and code, brand name, entry status, prescription status, composition status, and related ingredient codes.

Series: National Ambulatory Medical Care Survey Series

Access Notes

  • These data are freely available.


Dataset - Download All Files (6.5 MB)

Study Description


U.S. Dept. of Health and Human Services, National Center for Health Statistics. NATIONAL AMBULATORY MEDICAL CARE SURVEY, 1991. ICPSR version. Hyattsville, MD: U.S. Dept. of Health and Human Services, National Center for Health Statistics [producer], 1993. Ann Arbor, MI: Inter-university Consortium for Political and Social Research [distributor], 1995.

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Scope of Study

Subject Terms:   ambulatory care, doctor visits, health care services, medical care, medical evaluation, medical records, medications, patient care, patients, physicians, prescription drugs, treatment

Geographic Coverage:   United States

Time Period:  

  • 1991

Date of Collection:  

  • 1991

Universe:   Office visits made within the United States by patients of nonfederally-employed physicians who were primarily involved in office-based patient care activities, but not engaged in the specialties of radiology, pathology, or anesthesiology.

Data Types:   survey data and administrative records data

Data Collection Notes:

Per agreement with NCHS, ICPSR distributes the data file(s) and technical documentation in this collection in their original form as prepared by NCHS.


Sample:   The 1991 NAMCS sample included 2,540 physicians: 2,276 medical doctors and 264 doctors of osteopathy. The survey utilized a multistage probability sample design. Primary sampling units were selected in the first stage, physician practices within PSUs in the second stage, and patient visits to selected physicians in the third stage.

Data Source:

patient visit records completed by physicians


Original ICPSR Release:  

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