In 29 patients with stable ischaemic heart disease, right heart catheterization was performed to assess the effect of exercise and nitroglycerin on right ventricular volumes, which were determined by a new computerized thermodilution system. The coefficient of variation for the determination of right ventricular ejection fraction averaged 11.0 +/- 6.2% (mean +/- standard deviation) at rest and 14.6 +/- 8.1% during exercise. End-diastolic volume index increased from 90 (65-127) ml/m2 [median (range)] at rest to 101 (81-130) ml/m2 (P less than or equal to 0.0001) during exercise. Nitroglycerin reduced this parameter at rest to 77 (44-121) ml/m2 (P less than or equal to 0.05), without affecting exercise values. Resting right ventricular ejection fraction (55 [44-64]%) was diminished by both exercise (to 52 [39-62]%, P less than or equal to 0.05) and nitroglycerin (to 53 [40-65]%, P less than or equal to 0.05). Additionally, nitroglycerin reduced the exercise induced decrease of right ventricular ejection fraction from -3 (-20-10)% to -1 (-15-14)% (P less than or equal to 0.01). Nitroglycerin diminished the left-to-right interventricular end-diastolic pressure gradient, which was estimated from the difference between pulmonary capillary wedge pressure and right atrial pressure, at rest from 6 (1-17) mmHg to 5 (2-14) mmHg (P less than or equal to 0.05) and during exercise from 17 (6-31) mmHg to 14 (1-33) mmHg (P less than or equal to 0.001). It is concluded, that both exercise and nitroglycerin cause significant changes in right ventricular volumes.(ABSTRACT TRUNCATED AT 250 WORDS)