Stephen James Maassen, MD
Family Medicine Physician · Oshkosh, WI
Stephen James Maassen, MD is a family medicine physician with a practice address in Oshkosh, Wisconsin, and NPI 1972610426, issued on Aug 23, 2006. Check the license (Wisconsin 25987, as entered in NPPES) on the Wisconsin Medical Examining Board; the federal record below is the public data PlainDoctor holds for this provider.
- Name
- Stephen James Maassen
- Credential
- MD
- Primary taxonomy
- Family Medicine Physician 207Q00000X
- License number
- 25987 WI
Self-reported in NPPES; status is on the state search - Practice location
- 855 N Westhaven Dr, Oshkosh, WI 54904
- Phone
- (920) 303-8700
- Enumerated
- Aug 23, 2006
- Record last updated
- Mar 7, 2023
- Fax
- (920) 303-8832
- Medicaid ID
- 32829300 WI
- Entity
- Type 1 · individual
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Verify Stephen James Maassen in five checks
- 1IdentityNPI record in CMS NPPESNPI lookupConfirmed in NPPES
- 2LicenseActive license and public ordersWisconsin Medical Examining Board
Search for license 25987Check the board - 3Other statesLicenses and actions elsewhereDocInfo (FSMB)Not checked
- 4ExclusionsMedicare and Medicaid bansHHS-OIG exclusion listNot checked
- 5CertificationBoard certificationABMS AOA NCCPA AANPNot checked
Stephen James Maassen among 3,765 family medicine physician records in Wisconsin
Stephen James Maassen, MD is one of 3,765 family medicine physician records with a practice address in Wisconsin. 75% of them appear in a Medicare file (Part D prescribing, MIPS, Open Payments or Medicare group billing); this one does not. Its NPI, issued in 2006, is newer than 10% of them.
- NPI issued2006 · 10% of these records are older, 46% newer
- In a Medicare fileNo · 75% of these records are
- In the CMS Doctors and Clinicians fileNo · 62% of these records are
- Record last updated2023 · 56% of these records were not updated in five years or more
Source: CMS NPPES, file of Aug 9, 2026, every record with primary taxonomy 207Q00000X and a Wisconsin practice address; Medicare files: CMS Part D Prescribers 2024, MIPS 2023, Open Payments 2024, Doctors and Clinicians (data.cms.gov).
52 family medicine physician records list a practice address in Oshkosh
They are 52 of the 1,527 NPPES records with a practice address in Oshkosh, and 3,765 family medicine physician records in Wisconsin. No Medicare prescribing, quality score, industry payment or hospital affiliation is published for this NPI.
All 3,765 in Wisconsin → Every provider in Oshkosh → Family Medicine Physician nationwide →
The 8 family medicine physician records with the nearest ZIP codes
- Jon Carlson, MDOshkosh, WI 549041639188782
- Matthew Fischer, MDOshkosh, WI 549041962517011
- Pamela House, MDOshkosh, WI 549041851408470
- Rimas Janusonis, MDOshkosh, WI 549041558389890
- Daniel Kaiser, MDOshkosh, WI 549041437133824
- Michael Knier, MDOshkosh, WI 549041861509309
- Phyllis Lee, MDOshkosh, WI 549041124010749
- Gregory Long, MDOshkosh, WI 549041720008881
Common questions
What is Stephen James Maassen, MD's NPI number?
Stephen James Maassen, MD's National Provider Identifier (NPI) is 1972610426, issued on Aug 23, 2006. An NPI identifies a provider in billing; it is not a license.
Where is Stephen James Maassen, MD located?
The NPPES record lists a practice address at 855 N Westhaven Dr, Oshkosh, WI, 54904. Phone: (920) 303-8700. Providers update this record themselves, so call before visiting.
How can I verify Stephen James Maassen, MD's license?
NPPES lists Wisconsin license number 25987, as entered by the provider. Search the Wisconsin Medical Examining Board at https://dsps.wi.gov/Pages/BoardsCouncils/MEB/Default.aspx. The NPPES record confirms identity only; the state search shows license status, expiration and public orders.
Source: CMS National Plan and Provider Enumeration System (NPPES), file of Aug 9, 2026 (NPPES files on CMS.gov); NUCC Health Care Provider Taxonomy. An NPI identifies who bills; it is not a license.
Figures on PlainDoctor are read from the federal files each page names (CMS NPPES, Medicare Part D, MIPS, Open Payments; the HHS-OIG exclusion list only as counts) and from Census population estimates, with the file date shown beside them. See our editorial standards & corrections policy, the methodology behind these numbers, or report a data error. Data current as of Aug 9, 2026.