Circulating tumors cells (CTCs) and circulating endothelial cells (CECs) are found in the peripheral blood of most common malignancies and are promising surrogate biomarkers. The CellSearchTM CTC assay is currently approved by the Food and Drug Administration as an adjunct for monitoring disease status in breast, prostate and colon carcinomas; and evidence in breast cancer suggests that CTCs are an independent predictor of overall survival and progression-free survival. Evolving data demonstrates a potential role of CTCs as a surrogate assessment for treatment response. The benefit of this approach in renal cell cancer(RCC) is unknown and further investigation is needed to determine the feasibility of using the CellSearchTM CTC Assay in this malignancy.