To examine the "adequacy" of basal coronary flow in ventricular hypertrophy, the relation between proximal coronary artery dimensions and regional ventricular mass in aortic valve stenosis (AS) and hypertrophic cardiomyopathy (HC) was evaluated. Coronary artery size was determined by quantitative coronary arteriography while global/regional ventricular mass was calculated using computer-processed biplane 2-dimensional echocardiography. In comparison to 18 "normal" subjects, left anterior descending coronary dimensions were significantly larger in those with hypertrophy (normal 3.32 +/- 0.54, AS 3.82 +/- 0.71, HC 4.72 +/- 0.81 mm, p less than 0.05), with progressive increases in left anterior descending/circumflex coronary diameter ratios (normal 1.04 +/- 0.14, AS 1.18 +/- 0.19, HC 1.25 +/- 0.31, p less than 0.01). Compared to the AS group, indexed anteroseptal mass was greater in the HC subjects (AS 40.9 +/- 8.9 vs HC 72.1 +/- 21 g/m2, p less than 0.001). Both septal width/left anterior descending coronary diameter ratios (AS 3.61 +/- 1.06 vs HC 4.85 +/- 1.17 mm/mm, p less than 0.05) and indexed anteroseptal mass/left anterior descending coronary diameter ratios (AS 11.2 +/- 3.0 vs HC 15.6 +/- 3.4 g/m2/mm, p less than 0.01) were greater in HC subjects. Increased coronary dimensions were observed in both AS and HC, with the greatest changes noted within the left anterior descending distribution in HC, but when analyzed with respect to regional ventricular mass, these subjects demonstrated relative "inadequate" enlargement in coronary artery diameters. Underdeveloped epicardial coronary arteries may contribute to anteroseptal myocardial ischemia, with resultant angina pectoris, increased ventricular ectopic activity and sudden death in HC.