At A Glance

Noteworthy Characteristics

  • Height, weight, and obesity status are recorded on outpatient department patient records.
  • Diet/nutrition, exercise, and weight reduction counseling are noted on outpatient department patient records.
  • Nationally representative sample.
  • Includes children’s hospitals.



To collect data about the provision and use of ambulatory care services in hospital emergency departments, in the United States (U.S.).

Target Population

Patients visiting ambulatory care facilities, including emergency rooms at noninstitutional general and short-stay hospitals, exclusive of federal, military, and Veterans Administration hospitals, in all 50 states and the District of Columbia.


Began in 1992 and is still being conducted annually. The most recent data that are available is 2017.


National Center for Health Statistics, Centers for Disease Control and Prevention, U.S. Department of Health and Human Services

Special Note(s)

Unit of analysis is patient visit rather than the patient. Patients may visit the facilities multiple times during the survey period, but each visit is counted separately.

Data collection from outpatient departments, hospital ambulatory surgery centers (starting in 2009) and freestanding ambulatory surgery centers (starting in 2010) continued until 2017. Beginning in 2018, NHAMCS collected emergency department data only.

System Contact: Esther Hing []

See also: National Ambulatory Medical Care Survey (NAMCS)


Sample Design

Cross-sectional survey.

Four-stage probability sampling design. Learn more.

Sample Size

In 2017, there was approximately 370 eligible emergency departments surveyed. Data for approximately 139,000,000 weighted visits was collected. Learn more.

Special Note(s)

The NHAMCS sample selection procedure involves multiple stages in which representative participants are selected from increasingly specific strata. In the first stage, geographically defined areas are sampled. In the second stage, hospitals within these areas are sampled. In the third stage, clinics within outpatient departments are sampled. All emergency service areas and in-scope ambulatory surgery locations are included. In the final stage, patient visits to these settings are sampled.

The freestanding ambulatory surgery facility sampled includes visits to facilities that are regulated by states, certified by the Centers for Medicare and Medicaid Services, or whose primary business is ambulatory surgery. A two-stage list sample design is used for freestanding ambulatory surgery facilities (facilities, then patient visits to these facilities).

To preclude facilities from participating during the same time period each year, samples are randomly divided into 16 subsets of approximately equal size. Each subset is assigned one of 16 4-week reporting periods. These continue to rotate across each survey year. Therefore, the entire sample does not participate in a given year, and each hospital is inducted approximately once every 15 months.

Key Variables


NameMethods of Assessment
Patient race/ethnicityInterview/questionnaire (physician)
Patient sexInterview/questionnaire (physician)
Patient year of birthInterview/questionnaire (physician)


NameMethods of Assessment
Diet/nutrition counseling provided during visitInterview/questionnaire (outpatient department visits only)
Lipoprotein cholesterol, blood sugar, and glycohemoglobin (beginning in 2010)Interview/questionnaire (outpatient department visits only)

Physical Activity-Related

NameMethods of Assessment
Exercise counseling provided during visitInterview/questionnaire (outpatient department visits only)


NameMethods of Assessment
Height and weightInterview/questionnaire (outpatient department visits only)
Obesity statusInterview/questionnaire (outpatient department visits only)
Weight reduction counseling provided during visitInterview/questionnaire (outpatient department visits only)


NameMethods of Assessment
Federal Information Processing Standard (FIPS) state code (restricted)N/A
FIPS county code (restricted)N/A
Metropolitan statistical areaN/A
Patient zip code (restricted)N/A


NameMethods of Assessment
DiagnosisInterview/questionnaire (physician)
Diagnostic/screening servicesInterview/questionnaire (physician)
Medication therapyInterview/questionnaire (physician)
Patient complaints/reason for visitInterview/questionnaire (physician)
ProceduresInterview/questionnaire (physician)
Types of providers seenInterview/questionnaire (physician)
Visit dispositionInterview/questionnaire (physician)

Data Access and Cost

Data Availability

Public-use data are available. Data also are available on CD.

Some data files are restricted. These files can be accessed by applying to the National Center for Health Statistics (NCHS) Research Data Center. Learn more.


Free of charge. Restricted data are fee-based. Set-up fee for restricted data is $750 per day. Learn more.

Special Note(s)

The most recent year for which data are available is not necessarily the most recent year this survey was conducted.


Geocode Variable(s)

Metropolitan statistical area; Federal Information Processing Standard (FIPS) state code (restricted), FIPS county code (restricted), patient zip code (restricted).

Existing Linkages

None reported.

Selected Publications


Branner CM, Koyama T, Jensen GL. Racial and ethnic differences in pediatric obesity-prevention counseling: National prevalence of clinician practices. Obesity 2008;16(3):690-694.

Eneli IU, Keast DR, Rappley MD, Camargo CA Jr. Adequacy of two ambulatory care surveillance systems for tracking childhood obesity practice patterns. Public Health 2008;122(7):700-707.

Rao G. Pediatric obesity-related counseling in the outpatient setting. Ambulatory Pediatrics 2005;5(6):377-379.