At A Glance

Noteworthy Characteristics

  • Nationally representative sample.
  • Data collected from pediatricians and other child care providers.
  • Measured height and weight available for some patients.



To collect data about the provision and use of medical services at ambulatory care facilities in the United States (U.S.).

Target Population

Patients visiting ambulatory care facilities in the U.S.


Began in 1973. Conducted annually since 1989. Data are available for 1973 to 1981, 1985, and every year since 1989. The most recent data available are from 2016.


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.

System Contact: Danielle Davis

See also: National Hospital Ambulatory Medical Care Survey (NHAMCS)


Sample Design

Cross-sectional survey.

Multistage probability sample design. Learn more.

Sample Size

In 2016, there was approximately 670 eligible physicians surveyed. Data for approximately 884,000,000 weighted visits was collected. Learn more.

Special Note(s)

For most years the NAMCS sample selection procedure involves multiple stages in which representative participants are selected from increasingly specific strata. Geographic primary sampling units (PSUs) are selected in the first stage. In the second stage, physician practices within PSUs are selected (using the American Medical Association [AMA] and American Osteopathic Association [AOA] directories as the sampling frame). A random sample of patient visits to selected physicians are selected in the third stage.

Since 2006, separate strata have been selected for the second through fourth stages:
Second stage:
• A sample of 104 community health centers (CHCs) within PSU from a frame of CHCs maintained by the Health Resources Services Administration.
• The CHC sample includes urban Indian Health service outpatient clinics.
Third stage:
• A sample of up to three clinicians (physicians, nurse practitioners, physician assistants, and nurse midwives) within CHCs.
Fourth stage:
• A random sample of patient visits to selected clinicians.

To preclude double sampling of CHC physicians, AMA/AOA sampled physicians verified as working in CHCs at the time of the survey are excluded from the survey.

The 2012 NAMCS sample design differs from that of previous years. For 2012, NAMCS utilized a stratified two-stage sample, with physicians selected in the first stage and visits in the second stage. List samples were used in order to produce separate estimates for individual states with the largest populations. The 34 most populous states were targeted for individual visit estimation. These include California, Texas, New York, Florida, Illinois, Pennsylvania, Ohio, Michigan, New Jersey, Georgia, North Carolina, Virginia, Washington, Massachusetts, Indiana, Arizona, Tennessee, Missouri, Maryland, Wisconsin, Minnesota, Colorado, Alabama, South Carolina, Louisiana, Kentucky, Oregon, Oklahoma, Connecticut, Iowa, Mississippi, Arkansas, Kansas, and Utah.

From 2006, when NAMCS added the CHC stratum, through 2011, visits to CHC-sampled physicians were included with visits to traditionally sampled office-based physicians on the NAMCS data files. Beginning in 2012, only visits to office-based physicians are included in the traditional NAMCS data files. Data from CHC visits to physicians as well as non-physician practitioners sampled as part of the CHC panel were released as a separate data product for 2012-2014.

Over the years, sample design variables and the format and content of NAMCS questionnaires have changed.

Key Variables


NameMethods of Assessment
Patient ageInterview/questionnaire (physician)
Patient race/ethnicityInterview/questionnaire (physician)
Patient sexInterview/questionnaire (physician)
Percent practice revenue from Medicaid and other sourcesInterview/questionnaire (facility staff)


NameMethods of Assessment
Lipoprotein cholesterol, blood sugar, and glycohemoglobin (beginning in 2010)Interview/questionnaire (physician or lab staff)
Nutrition counseling provided during visitInterview/questionnaire (physician)

Physical Activity-Related

NameMethods of Assessment
Physical activity counseling provided during visitInterview/questionnaire (physician)


NameMethods of Assessment
Sleep disorders: Sleep apneaInterview/Questionnaire with Physician


NameMethods of Assessment
Height and weightInterview/questionnaire (physician)
Obesity statusMeasured; interview/questionnaire (physician)
Weight reduction counseling provided during visitInterview/questionnaire (physician)


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 on physician visits are available. Combined CHC visit data are available as restricted data.

NAMCS physician data also are available on CD.

Data on physician practice characteristics, including number of physicians at facility, are restricted. These data 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.

Public-use files are released annually. Future CHC public-use files to be released will combine multiple years of data.


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 noted.

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.

Ma J, Xiao L, Stafford RS. Adult obesity and office-based quality of care in the United States. Obesity 2009;17(5):1077-1085.

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