Abstract: The Circulating Endothelial Cells (CECs) and their activated and resting subsets (aCECs and rCECs) represent extremely rare cell population that play important roles in vascular pathophysiology. Their number and function are modulated in several diseases involving vascular injury such as human tumors. Although, consensuses on the phenotypic definition of endothelial cells and on the optimal enumeration technique is lacking, the number of clinical studies that are based on the assessment of endothelial cells the types of analytical methods that are employed are rapidly expanding. The goal of the current study was to develop a rapid and sensitive flow cytometric method to quantify and characterize CECs (their subsets and the apoptotic fraction of cells. In total, 75 peripheral blood samples were collected from normal donors and were analyzed with a six-color flow cytometric technique for the simultaneous analysis of the cell phenotypes of CECs and circulating progenitors cells using the following monoclonal antibodies: CD146, CD34, CD45, CD106 and CD133. In addition, the samples were analyzed with using the gating strategy. Apoptotic CECs and dead cells were detected using Annexin V and 7-amino-actinomycin D staining, respectively. The results show that the described technique is a reliable tool to increase the knowledge of endothelial cell biology and can be easily applied to the study of many pathological conditions.