The coronary flow vasodilator reserve (CFVR) in the proximal segment of the anterior descending coronary artery was studied in 50 patients with diabetes mellitus (DM), by Doppler study via transesophageal approach. Group 1 included 39 patients with DM concurrent with Stages 1-2 arterial hypertension (AH), of them 14 patients were documented as having coronary heart disease (CHD) in the presence of coronary atherosclerosis (Subgroup 1A) and CHD was excluded in the remaining 25 patients (Subgroup 1B). Group comprised 11 patients with normal blood pressure (BP). For comparison, 6 healthy individuals were examined. CFVR was calculated as a ratio of the peak diastolic coronary flow (CF) velocity during infusion of dipyridamole (0.56 mg/kg) to the baseline CF. CDVR was significantly decreased as compared with the controls (2.07 +/- 0.73 in Subgroup 1A, 2.15 +/- 0.67 in subgroup 1B, 1.78 +/- 0.33 in Group 2, and 3.68 +/- 0.26 in the controls), this decrease being due to low CF velocities in hyperemia in the majority of patients in Subgroup 1A and Group 2 and to higher baseline CF velocity in most patients from Subgroup 1B. In Group 1 patients, CFVR was not linear with age, the duration of the disease, BP and HbA1 levels, but it was related to the carotid distensibility coefficient (rho = 0.60, p = 0.004) and to the blood level of total cholesterol (rho = -0.43, p = 0.0107). In Group 2 patients, the least CF velocities in the presence of vasodilatation were detectable in older patients and in patients with hypercholesterolemia. An all the patients with left ventricular hypertrophy (LVH) had decreased CFVR whose values with the myocardial mass index above 130 g/m2 were significantly less than those in the absence of LVH. Thus, the limited reserve of coronary vasodilatation was detectable in patients with DM irrespective of BP levels and the status of epicardial arteries and it was most pronounced in LVH and hypercholesterolemia. The impaired elastic properties of peripheral arteries in the presence of cholesterolemia may be regarded as a marker of the low reserve of coronary vasodilatation in patients with DM concurrent with AH.