is the largest all-payer inpatient care database in the United States, containing data on more than seven million hospital stays from approximately 1,000 hospitals. 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 data elements descriptions for the NIS.

Data element descriptions explain how the data element is coded in the HCUP databases, what the uniform values are, and State-specific coding practices. The descriptions are cumulative across all states and years of NIS data from 1988 to the current data year. Not all data elements in the NIS are uniformly coded across states. Please check the "State Specific Notes" section for each data element before analysis. In addition, not all data elements in the NIS are available from every state. Refer to the year-specific Introduction to the Nationwide Inpatient Sample for information on which states and data elements are included in each year of the NIS.

For a description of how HCUP data elements are coded, restriction on use, uniform values, and state-specific coding practices, check the corresponding boxes below and then click the "View Description of Data Elements".