Written and maintained by CASRAI Editorial Board
Last updated
The Healthcare Cost and Utilization Project (HCUP, pronounced “H-Cup”) is a family of healthcare databases and related software tools sponsored by the Agency for Healthcare Research and Quality (AHRQ). This guide is for researchers and research administrators who need to know which HCUP database matches a question and what the access path looks like. It puts all eight databases in one comparison and adds a question-to-database map. Facts are from AHRQ’s HCUP pages, checked 2026-11-07.
What HCUP is
HCUP is a Federal-State-Industry partnership. Its databases bring together the data collection efforts of state data organizations, hospital associations, private data organizations and the Federal government into encounter-level, all-payer healthcare data. AHRQ describes it as the largest collection of longitudinal hospital care data in the United States, with all-payer, encounter-level information beginning in 1988. “Encounter-level” means a row describes one hospital stay or visit, not a person followed across settings. AHRQ lists the research uses as cost and quality of health services, medical practice patterns, access to healthcare programs, and treatment outcomes at national, state and local market levels.
Who runs it and what it covers
AHRQ sponsors HCUP; the data come from the partner organizations listed on AHRQ’s HCUP Partners page. There are eight databases in two families: nationwide samples built for national estimates, and state databases that hold records from participating states.
| Database | Family | Starts | What AHRQ says it is |
|---|---|---|---|
| NIS, National (Nationwide) Inpatient Sample | Nationwide | 1988 | More than seven million hospital stays each year |
| KID, Kids’ Inpatient Database | Nationwide | 1997 | A nationwide sample of pediatric inpatient discharges |
| NASS, Nationwide Ambulatory Surgery Sample | Nationwide | 2016 | A set of ambulatory surgery databases |
| NEDS, Nationwide Emergency Department Sample | Nationwide | 2006 | National estimates of emergency department (ED) visits |
| NRD, Nationwide Readmissions Database | Nationwide | 2010 | Designed to support analyses of national readmission rates |
| SID, State Inpatient Databases | State | 1995 | The universe of inpatient discharge abstracts from participating states |
| SASD, State Ambulatory Surgery and Services Databases | State | 1997 | Ambulatory surgery and other outpatient services from hospital-owned facilities |
| SEDD, State Emergency Department Databases | State | 1999 | Hospital-affiliated ED visits that do not result in hospitalization |
For the emergency department sample in detail, see CASRAI’s guide to NEDS (Nationwide Emergency Department Sample).
Which HCUP database fits which question
This mapping is editorial interpretation drawn from the descriptions in the table above, not an AHRQ recommendation.
- Readmission rates nationally: NRD, the database AHRQ describes as designed for that purpose.
- Pediatric inpatient care: KID, the nationwide pediatric inpatient sample.
- Emergency department visits nationally: NEDS. For ED visits that did not lead to hospitalization, in participating states, SEDD covers exactly that group.
- Ambulatory surgery: NASS for national estimates (from 2016), SASD for state-level surgery and outpatient services from hospital-owned facilities.
- All inpatient stays nationally, with the longest history: NIS, which starts in 1988.
- Inpatient discharges in participating states: SID.
How to obtain HCUP data
Many HCUP databases are available for purchase through the HCUP Central Distributor. AHRQ’s ordering page describes three steps:
- Create an online account on the Central Distributor (the ordering site is called CDORS).
- Complete the HCUP training and the HCUP Data Use Agreement. All purchasers and users must complete the web-based course, which covers data protection and individual responsibility, and receive a certification code that is required to purchase or access data. The course has interactive and Section 508 text-only versions.
- Purchase the databases from the databases page on CDORS.
Nationwide and State databases have separate Data Use Agreements, and signed documents are handled through CDORS. The restrictions themselves are written in the linked agreements; read them before planning an analysis. For the general concept, see Data Use Agreement (DUA).
HCUP database cost
There is no single HCUP price. Each HCUP data organization sets its own price, listed on CDORS, and some reduce it for AHRQ grantees, students or non-profits. The data organizations also decide what State-level data, if any, are available through the Central Distributor. AHRQ’s contact for questions is [email protected].
HCUP login
The ordering account is the CDORS account created in step 1; AHRQ’s HCUP pages link to the Central Distributor, where sign-in is found.
Free tools built on HCUP
- HCUPnet: a free online query system giving health statistics on hospital inpatient and emergency department use.
- HCUP Fast Stats: an online query tool with visual displays comparing national or state statistics, such as trends by payer and opioid-related hospital and ED use.
- AHRQ Quality Indicators: measures of healthcare quality built on hospital inpatient administrative data, with software and user guides for three modules.
- Clinical Classifications Software (CCS): a method for grouping diagnoses or procedures into clinically meaningful categories, developed with HCUP data.
For comorbidity adjustment, see the Elixhauser Comorbidity Index guide and, for the alternative measure, the Charlson Comorbidity Index.
Strengths and limits
Strengths follow from AHRQ’s description: all-payer coverage, a uniform format with privacy protections, encounter-level detail, a history back to 1988 for the inpatient sample, and a mix of national and state files. Limits are editorial interpretation: the unit is the encounter rather than a person, the databases are administrative hospital records, and what AHRQ describes covers inpatient, emergency department and hospital-owned or hospital-affiliated ambulatory settings. A question needing clinical measurements, or care outside those settings, needs another source.
Alternatives and neighbours
| Source | What it is | When it is a different tool |
|---|---|---|
| SEER Program | NCI’s system of population-based cancer registries | Cancer incidence, stage and survival rather than hospital encounters; see SEER coverage and data use |
| Individual state data organizations | The partners that supply HCUP’s state data | HCUP states that these organizations decide what State-level data, if any, are sold through the Central Distributor |
FAQ
What is HCUP data?
Encounter-level, all-payer hospital care data compiled in a uniform format, beginning in 1988, from state data organizations, hospital associations, private data organizations and the Federal government.
What is HCUP NIS?
The National (Nationwide) Inpatient Sample, which AHRQ describes as containing data on more than seven million hospital stays each year, starting with 1988.
What is the HCUP Central Distributor?
The channel through which many HCUP databases are bought. Ordering runs through CDORS after account creation, training and a Data Use Agreement.
Is HCUP free?
The databases are purchased, at prices set by each data organization. Tools such as HCUPnet and Fast Stats are free online query tools.
What are HCUP tools?
Software and products built on HCUP data, including HCUPnet, Fast Stats, the AHRQ Quality Indicators and Clinical Classifications Software. AHRQ’s Tools and Software page lists more.
Sources
- AHRQ, HCUP Overview (checked 2026-11-07).
- AHRQ, HCUP Central Distributor (checked 2026-11-07).
- AHRQ, HCUP Data Use Agreement training (checked 2026-11-07).
