Biplane cineventriculograms of the right ventricle at rest and during exercise were made of 16 patients with a right coronary artery stenosis of greater than 50% and less than 90% to explain the alteration of the volumes and function of the right ventricle during exercise-induced angina pectoris. The right ventricular enddiastolic volume increases from 113 +/- 6.6 ml/m2 to 133.9 +/- 9.8 ml/m2 (P less than 0.001). The endsystolic volume increases from 48.9 +/- 4.1 ml/m2 to 52.9 +/- 5.3 ml/m2. The stroke volume index increases from 64 +/- 5.5 ml/m2 to 81 +/-8.3 ml/m2 (P less than 0.001). At the same time the ejection fraction increases from 56.5 +/- 2.9% to 60.2 +/- 3.2% (P less than 0.05). The left ventricular enddiastolic pressure increases from 12.8 +/- 1.5 mm Hg to 26.6 +/- 1.6 mm Hg (P less than 0.001). The enddiastolic pressure of the right ventricle increases from 5.8 +/- 0.5 to 12.2 +/- 0.8 mm Hg (P less than 0.001). The mean velocity of diameter shortening, VD, increases from 0.9 +/- 0.06 D/s to 1.12 +/- 0.09 D/s (P less than 0.05). Exercise-induced angina pectoris leads to a considerable increase of the left ventricular enddiastolic pressure and therefore to an increase of the right ventricular afterload. The increase of afterload in patients with a right coronary artery stenosis is compensated by a considerable increase of the enddiastolic volume: the pump-function during exercise-induced angina pectoris is maintained by an increase of preload.