The National (Nationwide) Inpatient Sample (NIS) is the largest all-payer inpatient care database in the United States, containing data on more than seven million hospital stays. Its large sample size is ideal for developing national and regional estimates and enables analyses of rare conditions, uncommon treatments, and special populations.

The following links provide detailed documentation for the NIS, from a high-level Overview to all the detailed specifications, restrictions, and resources necessary for researchers working and publishing with the NIS.