This study is a prospective study carried on 32 Down syndrome patients collected from genetics clinic in the Children Hospital, Cairo University and 20 control children. The aim of this study was to compare the level of circulating progenitor stem cells in the blood of DS patients compared to controls, the relation between the level of EPCs and physical, mental development of DS patients and to correlate between numbers of circulating progenitor cells and capacity for tissue repair in DS patients. In this study, DS patients counted for detailed medical history including gestational age, sex, weight, height, paternal age, maternal age. There was no statistical significance as regard age, weight of Down syndrome patients compared to controls. There was statistical significance as regard height and IQ test. Also, there was statistical significance as regard VEGF in plasma of Down syndrome patients compared to controls. There was statistical significance as regard endothelial progenitor cells surface markers in 1000 peripheral blood mononuclear cells compared to controls.