BACKGROUND The relationship between the site of aortic valve thickening and ipsilateral coronary artery stenosis has not been reported previously. This study was undertaken to test the hypothesis that left-sided coronary cusp thickening may be associated with a left-sided coronary artery stenosis, and also as would be in the right-sided relationship. METHODS Two-dimensional echocardiography and cardiac catheterization were used to evaluate 420 consecutive patients. One hundred and six patients who had echocardiographic evidence of a single aortic valve thickening were studied to determine whether there was a relation between the coronary artery stenosis and the aortic valve thickening at the same side. Thickened aortic valve was defined as an aortic valve thickness to aortic wall thickness ratio > or = 1.0. Coronary artery disease (CAD) was defined as a > 50% luminal diameter narrowing of the left main coronary artery or a > 70% luminal diameter narrowing of the coronary artery other than the left main coronary artery. RESULTS Patients with a thickened aortic valve had a greater incidence of CAD (89/132, 67.4%) than those without (141/288, 49.0%) (p < 0.05). In patients with thickened aortic valves, the incidence of CAD was 45.5% in the fifth decade, 60% in the sixth decade, 69.6% in the seventh decade and 74.1% in the eighth decade. Progressive increase of the incidence of CAD was not found in patients without a thickened aortic valve. In the 106 cases with a single aortic valve thickening, 30 patients (28.3%) had a left coronary cusp thickening; 12 of them (40%) had a left-sided coronary artery stenosis, 3 patients (10%) had right coronary artery stenosis and 7 patients (23.3%) had no coronary artery stenosis. In the 34 patients with right coronary cusp thickening, the stenosis occurred at the left coronary artery in 13 patients (38.2%), at the right coronary artery in 3 patients (8.8%) and with normal coronary artery in 5 patients (14.7%). This finding did not support the relationship between thickened aortic valve and coronary artery disease at the same side (chi 2 = 0.06, p = 0.96). CONCLUSIONS There was a significantly greater incidence of CAD in patients with a thickened aortic valve than in those without. The incidence of CAD in patients with thickened aortic valves increased with age. There was no direct relationship observed between the site of aortic valve thickening and ipsilateral coronary artery stenosis.