Abstract： Objective　To investigate the changes and its clinical significance of plasma neuropeptide Y(NPY) concentration in patients with pregnancy induced hypertension (PIH). Methods　Plasma NPY levels were detected by radioimmunoassay in 30 patients with PIH, 20 normal non-pregnant women and 23 normal pregnant women. The PIH group was subdivided into mild, moderate and Severe subgroups, and the NPY concentration was also measured in these subgroups respectively at admission and one week after delivery. Results　The plasma NPY levels in patients with PIH ［(164.16±68.32) ng/L］ were significantly higher than those of normal non-pregnant women and normal pregnancies ［(86.60±20.65) ng/L, (82.42±12.46) ng/L, P<0.01, respectively］. There was significant difference among plasma NPY levels among the patients with mild, moderate, and severe PIH at admission (P<0,01). At one week after delivery the concentrations of plasma NPY were significantly decreased in the moderate and severe subgroups compared with the value measured at admission (P<0.01). Moreover, the NPY levels in patients with severe PIH after delivery were still higher than those of normal non-pregnant women. Conclusions　The results suggested that the level of NPY in plasma is increased in women with PIH. Elevated plasma NPY levels may play a key role in the development of PIH.