The Integrated Health Interview Series (IHIS) is a harmonized set of data and documentation based on material originally included in the public use files of the U.S. National Health Interview Survey (NHIS) and distributed for free over the internet.  IHIS currently consists of approximately 300 integrated variables selected from more than 2000 variables included in the core survey household and person files for 1969-2003, the sample adult/sample child files for
1997-2003, and the Access to Care supplements for 1993-96.