['This study sought to compare coronary artery dimensions in hypertensive patients and normal subjects.', 'Myocardial oxygen demand at rest and corresponding coronary blood flow are the main determinants of large coronary artery dimensions in humans. Coronary diameters are increased in aortic valve disease.', 'Left main, proximal and distal left anterior descending and proximal circumflex coronary artery diameters were measured by quantitative angiography in 10 control subjects (group 1) and 26 untreated hypertensive patients, 12 without (group 2a) and 14 with (group 2b) left ventricular hypertrophy. All patients had normal cholesterol levels and angiographically normal coronary arteries. Measurements were made at baseline and after 2 mg of intracoronary isosorbide dinitrate to obtain maximal dimensions of vessels. Coronary flow velocity was measured in the distal left anterior descending coronary artery by Doppler ultrasound.', 'Despite a higher rate-pressure product in hypertensive patients, all segment diameters were slightly but not significantly higher at baseline in group 2b than in groups 1 and 2a. Diameters were similar in the three groups after isosorbide dinitrate. Conversely, coronary flow velocity was significantly higher in hypertensive patients than in group 1 either at baseline (10.4 +/- 2.2 [mean +/- SD] cm/s [group 2a] and 12.8 +/- 2.4 cm/s [group 2b] vs. 6.5 +/- 2.0 cm/s [group 1], all p < 0.001) or after isosorbide dinitrate (6.8 +/- 2.8 cm/s [group 2a] and 7.8 +/- 2.1 cm/s [group 2b] vs. 3.7 +/- 0.8 cm/s [group 1], p < 0.01 and p < 0.001, respectively).'] Are epicardial coronary arteries adequately sized in hypertensive patients?