The aim of the study was to estimate the influence of drinking chokeberry juice on the endothelial function in men with mild hypercholesterolemia. It was shown that chronic treatment with flavonoids improves vascular function and reduces cardiovascular remodelling by increasing NO release from endothelial cells. A group of 35 men diagnosed with mild hypercholesterolemia (mean age: 53.9 +-5.8 years), with no earlier pharmacological treatment, were enrolled to the study. In all men, assessment of endothelial function, and serum lipids level were carried out at four time points: at the beginning of the studies, after 6 weeks of regular drinking of chokeberry juice, after 6 weeks without drinking the juice, then after repeated 6 weeks of drinking chokeberry juice. During the study, significant decreases in serum total cholesterol, LDL cholesterol and triglycerides levels were observed. A statistically significant increase in serum nitric oxide (NO) concentration and in the flow mediated dilatation (FMD) were observed. At the beginning, FMD > or = 7 % was present in 13 of 35 subjects (37.1 %). After 6 weeks of regular chokeberry juice drinking, FMD > or = 7 % was present in 29 of 35 subjects (82.9 %). However, after 6 weeks abstaining from drinking the juice and repeated exposure to 6 weeks drinking of chokeberry juice, FMD > or = 7 % was present in all studied subjects. Regular drinking of chokeberry juice has a beneficial effect on endothelial function and lipid metabolism in men with mild hypercholesterolemia.