National Archive of Computerized Data on Aging

National Hospital Ambulatory Medical Care Survey, 2008 (ICPSR 29922)

Principal Investigator(s):


The National Hospital Ambulatory Medical Care Surveys (NHAMCS) provide 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 2008 survey, data were colected from 209 OPDs and 431 EDs. Among the variables included are age, race, and sex of the patient, reason for the visit physician's diagnoses, cause of injury, surgical procedures (OPD's only), medication therapy, and expected source of payment. The 2008 survey remains unchanged from the previous year.

Series: National Hospital Ambulatory Medical Care Survey Series

Access Notes

  • These data are freely available.


WARNING: This study is over 150MB in size and may take several minutes to download on a typical internet connection.

DS1:  Emergency Department Data - Download All Files (216.4 MB) large dataset
Analyze Online:
DS2:  Outpatient Department Data - Download All Files (231 MB) large dataset
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Study Description


United States Department of Health and Human Services. Centers for Disease Control and Prevention. National Center for Health Statistics. National Hospital Ambulatory Medical Care Survey, 2008. ICPSR29922-v1. Ann Arbor, MI: Inter-university Consortium for Political and Social Research[distributor], 2011-01-18.

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Scope of Study

Subject Terms:   ambulatory care, emergency services, health care services, hospitalization, hospitals, injuries, medical care, medical evaluation, medical procedures, medical records, patient care, patients, payment methods, surgery, treatment

Geographic Coverage:   United States

Time Period:  

  • 2008

Date of Collection:  

  • 2008

Universe:   Visits to the emergency and outpatient departments of noninstitutional general and short-stay hospitals within the 50 states and the District of Columbia, which had an average length of stay of less than 30 days, or to hospitals whose specialty was general (medical or surgical) or children's general. Excluded were federal hospitals, hospital units within institutions, and hospitals with less than six beds staffed for patient use.

Data Types:   administrative records data

Data Collection Notes:

Per agreement with NCHS, ICPSR distributes the data file and text of the technical documentation for this collection as prepared by NCHS.

The Stata datasets (.dta files) made available by ICPSR do not contain all of the value labels found within the .do files supplied by ICPSR. Specifically, the value labels that are composed primarily of ICD-9 codes have been omitted from the .dta files. Those data users interested in applying the value labels to the datasets will be able to edit the Stata setup files, which include the aforementioned labels, provided by ICPSR.


Sample:   The National Hospital Ambulatory Medical Care Survey (NHAMCS) used a four-stage probability design with samples of primary sampling units (PSUs); hospitals within PSUs; clinics within hospitals; and patient visits within clinics.

Weight:   Microdata file users should be fully aware of the importance of the "patient visit weight" (PATWT) and how it must be used. Information about the patient visit weight is presented in the codebook. If more information is needed, the staff of the Ambulatory Care Statistics Branch can be consulted by calling (301) 458-4600.

Mode of Data Collection:   record abstracts

Data Source:

Patient visit records from hospital emergency departments and outpatient departments.

Response Rates:   90.2 percent unweighted, 89.8 percent weighted

Extent of Processing:  ICPSR data undergo a confidentiality review and are altered when necessary to limit the risk of disclosure. ICPSR also routinely creates ready-to-go data files along with setups in the major statistical software formats as well as standard codebooks to accompany the data. In addition to these procedures, ICPSR performed the following processing steps for this data collection:

  • Created variable labels and/or value labels.
  • Created online analysis version with question text.
  • Checked for undocumented or out-of-range codes.


Original ICPSR Release:  

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