AIM To observe the changes of plasma neuropeptide Y (NPY) levels in patients with essential hypertension(EH) taking Compound Qishao Jiangya Tablets (Radixet Rhizoma Notoginseng, Radix Paeoniae Alba, Rhizoma Gastrodiae, etc) and to investigate the significance of NPY in the pathogenesis of hypertension and the relationship between NPY and platelet disnormal function. METHODS The plasma NPY concentrations of 60 patients with EH and 20 normal ones were determined by radioimmunoassay, at the same time detected platelet aggregation rate and fibrinogen were detected. RESULTS The levels of plasma NPY in patients with EH were higher than that in normal control group. The NPY levels, the platelet aggregation rate, fibrinogen in the three periods of hypertension (period Ⅰ,Ⅱ, Ⅲ) were all significantly different and were increased with the severity of hypertension. CONCLUSION NPY may participate in the pathophysiological course of hypertension, and the plasma NPY, the platelet aggregation rate of the patients with EH were correlative. The plasma NPY should be dynamscally monitored in order to determine the disease degree. During the treatment for EH attention should be taken to decrease the platelet aggregation rate.