Hypertensive individuals occasionally experience angina-like chest pain despite having angiographically normal coronary arteries, and the etiology of this phenomenon has been suggested to be associated with depressed coronary flow reserve (CFR). Carotid intima-media thickness (IMT) assessed by ultrasound is correlated with not only cerebrovascular disease but also coronary artery disease and left ventricular hypertrophy (LVH). The aim of our study was to investigate the association between CFR and carotid IMT in patients with essential hypertension. We performed transthoracic Doppler recording of diastolic coronary flow velocity in the left anterior descending coronary artery at baseline and after maximal vasodilation by adenosine triphosphate infusion in 24 normotensive subjects and 125 hypertensive patients. CFR was defined as the ratio of hyperemic to basal averaged peak coronary flow velocity. Common cardiovascular risk factors, left ventricular mass index (LVMI), relative wall thickness (RWT), and carotid IMT were evaluated. The CFR of hypertensive patients (2.55 +/- 0.52) was significantly decreased compared with that of normotensive subjects (3.15 +/- 0.45). CFR showed a significant correlation with age, systolic blood pressure, RWT, and carotid IMT. Stepwise regression analysis revealed that, among carotid IMT, LVMI and RWT, only carotid IMT was a strong and independent parameter for predicting CFR in hypertensive patients. In conclusion, B-mode ultrasound scanning of the carotid artery seemed to be of clinical value in the screening of patients with LVH and impaired microcoronary circulation. These associations may explain the links between cardiac and cerebrovascular involvements in patients with hypertension.