 1. Flow cytometry after direct immunolabelling of whole blood or the mononuclear cell fraction using monoclonal antibodies and viability marker 7AAD. Due to the lack of specific markers for EPC and the great heterogeneity of cells that recovered the features of EPC21 flow cytometry analysis will include the numeration of different cell populations corresponding to differentiation state of EPC: CD34CD133 cells and CD34KDR cells. The circulating haematopoietic progenitors CD34CD45 will be also numbered.- 