Type 1 · Individual ✓ Active NPI ✓ Valid NPI checksum
Mr. William Michael Cassidy, MD
Pediatrics Physician in Vienna, VA · enumerated 2006.
Data current as of Jul 13, 2026 · sourced from CMS NPPES
National Provider Identifier
1740260306
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Registry record
Entity type Individual (Type 1)
Name Mr. William Michael Cassidy
Credential MD
Sex Male
Practice address 410 Maple Ave W, 5, Vienna, VA, 22180
Phone (703) 938-2244
Fax (703) 938-3669
Enumeration date Jan 19, 2006
Last updated in NPPES Jul 8, 2007
Taxonomy & licenses
208000000X Pediatrics Physician Allopathic & Osteopathic Physicians · License 0101026293 (VA) Primary
MD · Doctor of Medicine: A physician who completed medical school (allopathic medicine), residency training, and state licensure.
About the MD credential
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.
Frequently asked questions
What is the NPI number for William Cassidy?
The National Provider Identifier (NPI) for William Cassidy is 1740260306, a Type 1 (individual) record in the CMS NPPES registry.
Where does William Cassidy practice?
The practice location on file with NPPES is in Vienna, VA. Providers can have multiple locations; NPPES lists the primary practice address.
Other providers at this practice address
Browse all → Aaron Lopata Pediatrics Physician · Vienna, VA NPI 1144292632 Peggy Thurston Nurse Practitioner · Vienna, VA NPI 1023077260 Virginia Gynecologists, Ltd Obstetrics & Gynecology Physician · Vienna, VA NPI 1962438119 Kanaka Sriram, D.D.S., P.C. General Practice Dentistry · Vienna, VA NPI 1104038546 Wendy Snyder Specialist · Vienna, VA NPI 1023224094 Jackie Stout Clinical Social Worker · Vienna, VA NPI 1518280536
Source: CMS NPPES (public data). Snapshot 2026-07-13. Provider record last updated 2007-07-08.