Type 2 · Organization ✓ Active NPI ✓ Valid NPI checksum

Robert O'Brien MD & Assoc.

Specialist in Winchester, MA · enumerated 2011 · authorized official Robert O'Brien, President.

Data current as of Jul 13, 2026 · sourced from CMS NPPES

National Provider Identifier

1598041410

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Registry record

Entity type Organization (Type 2)

Legal business name Robert O'Brien MD & Assoc.

Practice address 955 Main St, G6, Winchester, MA, 01890

Phone (781) 729-4878

Fax (781) 729-5989

Enumeration date Oct 24, 2011

Last updated in NPPES Oct 24, 2011

Taxonomy & classification

174400000X Specialist Other Service Providers · License 209962 (MA) Primary

Authorized official

Name Robert O'Brien

Title President

Phone (781) 729-4878

What is an NPI number?

A National Provider Identifier (NPI) is a unique 10-digit number that CMS assigns to every U.S. healthcare provider and organization under HIPAA. Type 1 NPIs identify individual providers; Type 2 NPIs identify organizations. The NPI appears on insurance claims, prescriptions, and credentialing paperwork, and never changes, even if the provider moves or changes specialty.

Read the full guide → Validate an NPI →

Frequently asked questions

Where is Robert O'Brien MD & Assoc. located?

The practice location on file with NPPES is in Winchester, MA.

How current is this record?

Data comes from the CMS NPPES public dissemination file; this record was last updated in NPPES on 2011-10-24. Verify at npiregistry.cms.hhs.gov.

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Source: CMS NPPES (public data). Snapshot 2026-07-13. Provider record last updated 2011-10-24.