Provider records sourced from NPPES (CMS National Plan & Provider Enumeration System). Data current as of October 4, 2026.
NPIDirectory

William M. Greif, MD

Individual provider Surgery Physician · NPI 1013095108

William M. Greif, MD practises General Surgery in Walnut Creek, California. Graduated from Stanford University School of Medicine in 1993, 33 years ago. Practices with Permanente Medical Group Inc, a 10,941-clinician group and accepts Medicare assignment. Licensed in California.

Years since qualifying
33
Trained at
Stanford University School of Medicine
Licensed in
CA
In the registry since
2006
What do these letters mean?
MD — Doctor of Medicine
A physician who completed allopathic medical school.

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Practice location Address checks out

1425 S Main St
Walnut Creek, CA 94596-5318
Phone: (925) 295-4000
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Pin is approximate — placed at the ZIP-code centre, not the exact door.

Specialties & licences

Surgery Physician (primary) Taxonomy 208600000X · Licence G85813 (CA)

Record details

NPI number1013095108
Entity typeIndividual (Type 1)
GenderMale
Credentials MD
Sole proprietorNo
NPI enumeratedNovember 2, 2006
Last updated in NPPESDecember 13, 2021

Medicare enrollment

From the CMS Doctors & Clinicians file — this clinician is enrolled in Medicare.

Medicare specialtyGENERAL SURGERY
Also practisesSURGICAL ONCOLOGY, THORACIC SURGERY, VASCULAR SURGERY
Medical schoolSTANFORD UNIVERSITY SCHOOL OF MEDICINE
Graduated 1993 (33 years in practice)
Group practice Permanente Medical Group Inc — 10941 clinicians
Accepts Medicare assignment Yes — accepts the Medicare-approved amount
Practice locations3 on file with Medicare

Procedures

From CMS Care Compare, which counts the procedures a clinician billed to Original Medicare and Medicare Advantage over a recent 12-month period. CMS reports a fixed list of common procedures, so this is not everything the clinician does. Counts of 10 or fewer are given as a range, because CMS withholds small numbers.

Mastectomy 1–10 times
Melanoma (skin cancer) excision 1–10 times
Removal of tissue 1–10 times

The percentile compares how often this clinician performed the procedure with other clinicians who performed it, as CMS calculates it. It measures volume, not outcomes or skill.

Colleagues at Permanente Medical Group Inc

Clinicians the CMS Doctors & Clinicians file lists under the same group practice. CMS counts 10941 clinicians in the practice; 12 are shown here.

Other providers in Walnut Creek