Background: Noninvasive biomarkers are needed for diagnosis, prognosis, and molecular profiling of HCC due to scarcity of tumor tissue and heterogeneous tumor biology. CTC are detectable in metastatic HCC using methods which enrich for expression of the cell adhesion molecule, EpCAM. Because a subset of HCC does not express EpCAM, however, non-EpCAM enrichment methods are needed for CTC studies in HCC. Methods: This CTC cohort was derived from patients enrolled on multicenter phase 1 and 2 trials of the combination of sorafenib plus temsirolimus in advanced HCC (NCT01008917, NCT01687673) with approval and funding from the National Comprehensive Cancer Network (NCCN) Oncology Research Program. Eligibility required histologic diagnosis of incurable HCC with no prior systemic therapy. All patients in the cohort were treated at the recommended phase 2 dose of sorafenib 200 mg PO BID and temsirolimus 10 mg IV weekly. Whole blood samples were collected at baseline and on treatment. CTC were enumerated and analyzed cytomorphologically using a high-definition, single cell assay without EpCAM enrichment and blinded to clinical outcomes. Results: The CTC cohort was comprised of 36 patients (phase 1 n = 9, phase 2 n = 27). Characteristics: male 89%; white 64%, Asian/PI 28%, black 6%; HBsAg+ 31%, HCV+ 44%; Child Pugh A 92%, B7 8%; BCLC C 83%; tumor vascular invasion 47%; median AFP 74 ng/mL. Median OS from start of treatment was 392 days (95% CI: 214, 569). CTC ≥ 1/mL were detectable at baseline in 23/36 (64%) overall (95% CI: 47%, 80%), with similar findings in the phase 1 (56%) and phase 2 (67%) subsets. There was no significant relationship between baseline CTC values ≥ 1, 2, or 5/mL and overall survival (OS) on univariate analysis. Analyses of CTC relationship to clinical characteristics and time to progression, changes on treatment, and multivariable analysis for relationship to OS will be presented. Conclusions: CTC were detected in over 60% of patients in this advanced HCC clinical trial cohort using a non-EpCAM, high-definition single cell assay, suggesting future potential for noninvasive molecular profiling of HCC.