This study investigates the effects of the Panax ginseng (Araliaceae) extract G115 on angiotensin-converting enzyme (ACE) activity and nitric oxide (NO) in cultured human endothelial cells from umbilical veins (HUVEC) and bovine mesenteric arteries (BMA). In HUVEC, ACE activity was significantly reduced after 10 min incubation with aqueous extract of ginseng 5.0 and 10 mg/ml. This effect was additative with the inhibition of the traditional ACE inhibitor enalaprilat. No effect was seen on NO production from the cells. Angiotensin I-induced contraction of BMA was significantly attenuated by 0.1 and 0.5 mg/ml ginseng, while no endothelium-dependent or -independent relaxation was seen. In conclusion, extract of Panax ginseng (G115) inhibits ACE activity, but does not affect NO production in HUVEC and BMA.