Quick answers
- Which hospitals does Mark D. Grossklaus work at?
- Medicare's official clinician data lists Mark D. Grossklaus at 2 hospitals: Oconomowoc Memorial Hospital and Waukesha Memorial Hospital. This is where the clinician works or has privileges; call the hospital to confirm.
- Where does Mark D. Grossklaus see patients?
- Medicare's clinician data lists 5 practice locations, including Waukesha, WI. Call before your visit to confirm the address.
- What is Mark D. Grossklaus's specialty?
- Medicare lists Family Practice as the primary specialty.
- Does Mark D. Grossklaus accept Medicare assignment?
- Yes. Medicare's clinician data says Mark D. Grossklaus accepts Medicare assignment (the Medicare-approved amount as full payment for covered services), as of 2026-10-02. Ask the office to confirm before your visit.
- What is the phone number for Mark D. Grossklaus?
- (262) 542-9100, as listed in official Medicare / NPI Registry data.
- What is Mark D. Grossklaus's NPI number?
- 1255403101. The NPI (National Provider Identifier) is the clinician's permanent federal ID; you can look it up in the official NPI Registry.
Hospitals where Mark D. Grossklaus works
Medicare's Facility Affiliation Data lists Mark D. Grossklaus at these hospitals (updated 2026-10-02). Each hospital page shows its address, phone, emergency services, Medicare rating and all its clinicians.
- Oconomowoc Memorial HospitalOconomowoc, WI · Acute Care Hospital · CCN 520062
- Waukesha Memorial HospitalWaukesha, WI · Acute Care Hospital · CCN 520008
Practice locations
Addresses where Mark D. Grossklaus is enrolled with Medicare (CMS data updated 2026-10-02).
- 717 W Moreland BlvdWaukesha, WI 53188 (262) 542‑9100
- N14W24100 Riverwood DrWaukesha, WI 53188
- N16W24131 Riverwood DrWaukesha, WI 53188 (262) 696‑0808
- N16W24131 Riverwood Dr, Suite 2200bWaukesha, WI 53188 (262) 696‑0765
- N17W24100 Riverwood DrWaukesha, WI 53188
Group practices
Medicare enrollment lists Mark D. Grossklaus as a member of this group (CMS data updated 2026-10-02).
- Prohealth Medical Group Inc479 clinicians in the group
Specialties
- Family Practiceprimary
Other family doctors in Waukesha
Clinicians with the same Medicare primary specialty in Waukesha, WI — not a recommendation.
Clinician information
| Credential | MD |
|---|---|
| Medical school | University Of Wisconsin School Of Medicine |
| Graduation year | 1994 |
| Gender (as listed) | Male |
| Medicare assignment | Accepts (Medicare-approved amount as full payment) |
| NPI (National Provider Identifier) | 1255403101 |
| Corrections | Report an error or suggest an update → |
Most corrections must be made at the source: clinicians update their NPI Registry record (NPPES) and their Medicare enrollment (PECOS); this page follows the next data release.
Sources
- Facility Affiliation Data — Centers for Medicare & Medicaid Services (CMS), data updated 2026-10-02, retrieved 2026-10-29
- National Downloadable File (Doctors and Clinicians) — CMS, data updated 2026-10-02, retrieved 2026-10-29
- NPI Registry — U.S. Department of Health and Human Services (NPPES), the clinician’s official record
- Medicare Care Compare — official Medicare tool to look up clinicians