The effects of Origanum onites on endothelial function and antioxidative status were investigated in 48 patients with mild hyperlipidaemia who required no drug therapy. All participants were given lifestyle and low-fat dietary advice, however 32 of the patients (study group) were also prescribed 25 ml of aqueous distillate of Origanum onites to be taken after each meal for 3 months. The remaining 16 patients were the control group. Various biochemical markers and endothelial function parameters were measured at baseline and after 3 months. A significantly greater increase in high density lipoprotein-cholesterol and significantly greater decreases in low density lipoprotein-cholesterol, apolipoprotein B, lipoprotein(a) and high sensitivity C-reactive protein occurred in the study group compared with the control group over the 3-month study period. Paraoxonase and arylesterase activities, and flow- and nitroglycerine-mediated dilatation of the brachial artery showed significantly greater increases in the study group compared with the changes in the control group. In conclusion, consumption of Origanum onites distillate had beneficial effects on lipid profiles, antioxidant status and endothelial function in patients with mild hyperlipidaemia.