Aim of the research was to detect and identify initial changes of elastic properties of magistral arteries (arterial stiffness). Flow mediated dilatation-(FMD) method was used to prove, i.e. to set hypothesis that the effects of strict dietary regime to endothelial function of brachial artery in patients with stable angina and atherosclerotic changes in coronary arteries less than 50% confirmed by coronarography will lead to significant increase of FMD values. Total 60 subjects aged 40-75 were enrolled in the study. Diet group consisted of 30 subjects with atherosclerotic changes in coronary arteries less than 50% confirmed by coronarography. Control group consisted of 30 subjects not receiving medical treatment. Following initial examination, follow-up was carried out after 3 and 6 months. As expected, the flow velocity following cuff release was higher at each measurement in both diet and control group compared to baseline values. Flow velocity following nitroglycerin administration in the diet group was insignificantly higher in both follow-ups, whereas it was lower in the control group in both second and third measurement. Analysis of variance results for relations within groups show no differences. On the basis of the obtained results, FMD measurements on brachial artery may contribute to early detection of atherosclerotic changes, especially in patients with multiple risk factors.