Abstract: Urinary norepinephrine （UNE） and epinephrine（UE） contents were measured in 60 cases of essential hypertension （EH） and 31 normal controls for evaluating the sympathetic activity. The mean 24 h,daytime and nighttime UNE inEH cases was significantly higher than that in normal su bjects（982. 54±373. 82 vs 724. 06±230. 70 nmol, 525. 86±242. 02vs 414. 03±130. 74 nmol,and 456. 68±203. 29 vs 310.04±141. 92 nmol, P ＜ 0. 01 ）, and no statistical difference wasfound in mean UE（24 h, daytime and nighttime） between EHcases and normal subjects （P＞0. 05 ）. The daytime UNE wassignificantly higher than nighttime UNE in normal subjects （P＜0. 01 ）, but such circadian rhythm disappeared in EH group（P＞ 0. 05）. Using the mean UNE value plus 2SD values ofthe normal controls as a upper limit, there were 19 cases （31.7%） and 12 cases （20%） of EH, whose 24 h and nighttimeUNE contents were higher than the cut-of f respectively. Thisstudy suggests the UNE content can be used as a index for assessrnent of the sympathetic activity in EH.