OBJECTIVES: To explore physician specialty patterns for the treatment of hepatocellular carcinoma (HCC).    METHODS: Medicare patients diagnosed with HCC in 2000-07 with >=1 claim for HCC-related physician visits post-diagnosis were studied through 2009 using SEER-Medicare data. Transplant patients were excluded. Visits by specialists seen within 4 weeks of diagnosis and by therapy within the first treatment week were explored. Specialties: Gastroenterology (GE), General/Family/Geriatric/Internal (GF), Diagnostic/Intervention radiology (DIR), Hematology/Medical oncology (HMO), General surgery/Surgery oncology (GSO), Radiation oncology (RO), Multispecialty clinic/group practice (MG), Others.  Therapies (non-mutually exclusive): surgical resection, percutaneous ablation, transarterial chemoembolization (TACE), bland embolization, systemic chemotherapy, selective internal radiation therapy, external beam radiation therapy.  We examined second-line therapy, specialists seen since week 5, and multiple-specialty visits as related to multiple-first-line therapies. RESULTS: Of 6472 patients with>=1 specialist, 25% saw GE, 10.5%GF, 23% DIR, 28%HMO, 16% GSO, 4% RO, 5.5%MG, and 66%Other; 52% saw >1 specialist type within 4 weeks of diagnosis, 5%none until after 4 weeks;  6% had a resection as first line, 8%ablation, 9%TACE, 0.7%TAE, 9%chemo, 1%SIRT, 8%EBRT; 64% were untreated; 46% of patients saw only 1 specialist type in the first 4 weeks and 4% got >1 therapy form in the first treatment week. The specialties distributions did not differ across first-line therapies. Other specialists were seen by 65% of patients. GE and HMO were the most common specialty: 21-29% of patients saw GE and 23-37% saw HMO, 20-24%DIR, 11-17%GSO, 9-13%GF, 4-6%RO, and 1%MG, across therapies.  Of the 2819 patients who saw only 1 type of specialist in the first 4 weeks, 52% visited Others, 13%GE, 11%HMO, 10%DIR, 6%GSO, 5%GF, 4%RO, and 0.4%MG.  CONCLUSIONS: HCC patients commonly see Gastroenterologists and Hematologists/Medical oncologists within 4 weeks of HCC diagnosis.  There was no clear HCC treatment pattern by specialist type.