Aim To investigate the gender differences in the levels of nitric oxide in prehypertension and its correlation with the number and function of circulating endothelial progenitor cells. Methods Eighty consecutive population, 46.4±4.3 years old, were divided into four groups:normotensive premenopausal women (n=21), prehypertensive premenopausal women (n=20), normotensive men (n=19) and prehypertensive men (n=20). The nitric oxide (NO), granulocyte-macrophage colony stimulating factor (GM-CSF) and vascular endothelial growth factor (VEGF) levels in plasma and secreted by circulating EPCs were measured in the four groups. Results The distribution of plasma NO level, the NO secretion by cultured EPCs in normotensive and prehypertensive premenopausal women were significantly higher than those in normotensive and prehypertensive men (P＜0.05). The plasma NO level or NO secretion by EPC in normotensive men was also higher than that in prehypertensive men (P＜0.05). However, the plasma NO level or NO secretion by EPC in normotensive premenopausal women was almost equal to that of prehypertensive premenopausal women (P＞0.05). The plasma NO level or NO secretion by EPC was related to the number or activity of circulating EPC. No significant difference was found in plasma VEGF or GM-CSF level in the four groups (P＞0.05). Conclusions The plasma NO level and NO secretion of circulating EPC were preserved in prehypertensive premenopausal women, which was correlated with the number and activity of circulating EPC.