NPI Portal NPI Lookup & Verification

Type 1 · Individual ✓ Active NPI ✓ Valid NPI checksum Sole proprietor

Dr. Robert James Mayer, MD

Medical Oncology Physician in Boston, MA · enumerated 2005 · practices at Dana-Farber Cancer Institute, Inc..

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

National Provider Identifier

1659361327

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Registry record

Entity type Individual (Type 1)
Name Dr. Robert James Mayer
Credential MD
Sex Male
Practice address Boston, MA, 02215
Phone (617) 632-3474
Fax (617) 632-2260
Enumeration date Oct 25, 2005
Last updated in NPPES Dec 7, 2011

Street address withheld: NPPES sole-proprietor addresses can be home addresses. See our data policy.

Taxonomy & licenses

207R00000X Internal Medicine Physician Allopathic & Osteopathic Physicians · License 36776 (MA) Secondary
207RH0000X Hematology (Internal Medicine) Physician Allopathic & Osteopathic Physicians · License 36776 (MA) Secondary
207RX0202X Medical Oncology Physician Allopathic & Osteopathic Physicians · License 36776 (MA) Primary
MD · Doctor of Medicine: A physician who completed medical school (allopathic medicine), residency training, and state licensure. About the MD credential

Other identifiers

Identifier Type State Issuer
M08749 Other MA BCBS MA
2038706 Medicaid MA -
730076 Other MA TUFTS HEALTH PLAN

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.

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Frequently asked questions

Where does Robert Mayer practice?
The practice location on file with NPPES is in Boston, MA. Providers can have multiple locations; NPPES lists the primary practice address.
What is the NPI number for Robert Mayer?
The National Provider Identifier (NPI) for Robert Mayer is 1659361327, a Type 1 (individual) record in the CMS NPPES registry.

Other providers at this practice address

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Source: CMS NPPES (public data). Snapshot 2026-07-13. Provider record last updated 2011-12-07.