To examine the changes in number and function of endothelial progenitor cells (EPCs) from peripheral blood (PB) in hypertension disorder complicating pregnancy (HDCP), 20 women with HDCP and 20 normal pregnant women at the third trimester were studied. Mononuclear cells (MNCs) from PB were isolated by Ficoll density gradient centrifugation. EPCs were identified by positive expression of both CD34 and CD133 under fluorescence microscope and positive expression of factor VIII as shown by immunocytochemistry. The number of EPCs was flow-cytometrically determined. Proliferation and migration of EPCs were measured by MTT assay and modified Boyden chamber assay, respectively. The adhesion activity of EPCs was detected by counting the number of the adherent cells. The results showed that, compared with normal pregnant women, the number of EPCs was significantly reduced in HDCP (4.29%+/-1.21% vs 15.32%+/-2.00%, P<0.01), the functional activity of EPCs in HDCP, such as proliferation (13.45%+/-1.68% vs 18.45%+/-1.67%), migration (37.25+/-7.28 cells/field vs 67.10+/-9.55 cells/field) and adhesion activity (20.65+/-5.19 cells/field vs 34.40+/-6.72 cells/filed) was impaired (P<0.01). It is concluded that the number and function of EPCs are significantly decreased in HDCP.