National Archive of Computerized Data on Aging

National Hospital Ambulatory Medical Care Survey, 2006 (ICPSR 28321)

Principal Investigator(s):


The National Hospital Ambulatory Medical Care Survey (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 2006 survey, data were collected from 236 OPDs and 464 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 (OPDs only), medication therapy, and expected source of payment. For 2006, additional updates and revisions have been made to both the emergency department and outpatient department data, including modifications to pre-existing variables and the inclusion of new variables pertaining but not limited to electronic medical record systems and diagnostic screening services.

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 (214.5 MB) large dataset
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DS2:  Outpatient Department Data - Download All Files (222.4 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, 2006. ICPSR28321-v1. Ann Arbor, MI: Inter-university Consortium for Political and Social Research [distributor], 2010-06-11.

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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:  

  • 2006

Date of Collection:  

  • 2006-01-02--2006-12-31

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:

Users should be aware that Stata will not allow value labels for character (string) format variables. The 2006 NHAMCS data contain a number of character variables (e.g., DIAG1, DIAG2, and DIAG3 -- physician's listed diagnosis codes).

A numeric recode version of the diagnosis variables (DIAG1R, DIAG2R, DIAG3R) has been included in the data. Value labels have been added to the SAS and SPSS setup files. Users may verify the labeling of the numeric recode variables by referring to the character (string) format variables DIAG1, DIAG2, and DIAG3. Please consult the User Guide for detailed information regarding numeric recodes for cause of injury, diagnosis, and procedure codes.

Per agreement with the National Center for Health Statistics (NCHS), ICPSR distributes the data files and text of the technical documentation for this collection as prepared by NCHS.

Detailed information regarding the use of weight variables and variance estimation is located in the User Guide.


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:   Users should use the variable PATWT when performing analyses.

Data Source:

Patient visit records from hospital emergency departments and outpatient departments.

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.


Original ICPSR Release:  

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