Nationwide inpatient sample (NIS)

The NIS is the largest publicly available all-payer inpatient care database in the United States. It contains data from approximately 8 million hospital stays each year. The 2012 NIS was redesigned. The new NIS is a sample of discharges from all hospitals participating in HCUP. For prior years, the NIS was a sample of hospitals. The NIS allows for weighted national estimates to identify, track, and analyze national trends in health care utilization, access, charges, quality, and outcomes.

The NIS contains clinical and resource use information included in a typical discharge abstract, with safeguards to protect the privacy of individual patients, physicians, and hospitals (as required by data sources). The NIS excludes data elements that could directly or indirectly identify individuals.

Alternative title
National inpatient sample (NIS)
National (nationwide) inpatient sample (NIS)
Data creator

Healthcare Cost & Utilization Project (HCUP)

U.S. Department of Health and Human Services. Agency for Healthcare Research and Quality

Healthcare Cost and Utilization Project (HCUP)
Geographic coverage

United States, participating states

Time period

Stratified probability sample of hospitals in the frame, with sampling probabilities proportional to the number of U.S. community hospitals in each stratum. The frame is limited by the availability of inpatient data from the data sources currently participating in HCUP. Target sample size is 20%


Healthcare Cost and Utilization Project (HCUP)

Date of collection
1988 to 2000
Mode of data collecton

Administrative records

Unit of observation
Hospitals, individual discharges

Available on CD-ROM at the Map & Data Library. Note the second release of the 1997 survey includes records that were omitted in the first release. 

Access status
Access conditions and restrictions

University of Toronto students, staff and faculty for research purposes only. Each user must sign a copy of the Data Use Agreement and complete the online Data Use Agreement Training Course at 

CD number
1228 (1988 data)
1229 (1989 data)
1230 (1990 data)
1231 (1991 data)
1232 (1992 data)
1233 (1988-1992 documentation)
1234 (1993 data)
1235 (1993 documentation)
1236 (1994 data)
1237 (1994 documentation)
1238 (1995 data)
1239 (1995 documentation)
1240 (1996 data)
1241 (1996 documentation)
1242 (1997 data)
1243 (1997 documentation)
1244 (1997 release 2 data)
1245 (1997 release 2 documentation)
1246 (1998 data)
1247 (1998 documentation)
1248 (1999 data)
1249 (1999 documentation)
1250 (2000 data)
1251 (2000 documentation)