Ambulatory Health Care Data

Notices for NAMCS and NHAMCS Public Use Data File Users

NHAMCS Outpatient Department Data from 2012-2017

Due to quality assurance issues, NHAMCS Outpatient Department (OPD) data from 2012-2017 are currently on hold. We are exploring whether these data can be released. Due to budget constraints, OPD data were not collected from 2018-2020.

Masked Design Variables

Currently, NAMCS public-use files for 1993-2016 and NHAMCS public-use files for 1992-2016 contain sample design variables in masked form. The initial release of the 2000-2016 public-use files includes masked sample design variables. We re-released the 1993-99 NAMCS and 1992-99 NHAMCS files to include these variables. For re-released files, file names and layouts are essentially the same, but the design variables were appended to each file according to a generic file layout that is available for downloading.

For 1993-99 NAMCS and 1992-99 NHAMCS, be sure to download not only the original file documentation for each year, but also the supplemental files that explain the new sample design variables that have been added to each file. The supplemental files also include descriptions of any revisions that may have been made to the original data files.

Data users should note that, beginning with the 2002 public use files, two new masked design variables were added to the file, for use with statistical software that assumes a single stage of sampling. For the 2003 public use files and beyond, the decision was made to include only these two masked design variables for variance estimation. Therefore, data users who wish to combine years of data from 2003 and beyond with years prior to 2002 will need to create these two variables for each file prior to 2002. A technical paper, Using Ultimate Cluster Models with NAMCS and NHAMCS Public Use Files pdf icon[PDF – 34 KB] gives instructions.

Possible Problems Downloading Data Files and Documentation

Some data users have experienced a problem when trying to open self-extracting compressed data files and documentation in .EXE format in survey years prior to 2003. They receive a message that the version of the file is not compatible with the version of Windows they are running. This is because the files were created when NCHS used a 32-bit version of Windows, but newer versions use a 64-bit version. One work-around for this problem involves the use of WinZip software. Save the file in your local directory as usual, but instead of double-clicking on the file name to access the data, right-click the file name, select WinZip and choose one of the options for file extraction. This will cause an uncompressed version of file to appear in the directory window. For the longer term, NCHS is working on producing a new version of the problem files. Please contact the Ambulatory and Hospital Care Statistics Branch if you have questions. (9/2014)

Supplemental Documentation Files for 1993-99 NAMCS and 1992-99 NHAMCS

For 1993-99 NAMCS and 1992-99 NHAMCS, be sure to download not only the original file documentation for each year, but also the supplemental files that explain the new sample design variables that have been added to each file. The supplemental files also include descriptions of any revisions that may have been made to the original data files.

Public Use Data File and Documentation Updates

Occasionally, revisions are made to either the Public Use Data Files or Public Use Data File Documentation.  Check these pages for more information:

Other Sources for NAMCS and NHAMCS Data

NAMCS and NHAMCS data can also be downloaded from the Inter-University Consortium for Political and Social Research (ICPSR)external icon.

Page last reviewed: June 11, 2019