The effect of steady-state exercise and of increased afterload by angiotensin infusion on the right ventricular function was examined in 21 patients with chronic obstructive lung disease (COLD). 15 of them were always free from cardiac failure and 6 of them have had clinical signs of failure at the time of examination. Despite significant differences in various parameters between compensated (C) and decompensated (D) subjects, only the right ventricular filling pressure during both experimental procedures was able to differentiate the majority of individual C and D patients. The authors discuss the mechanisms of haemodynamic response to both stress tests and their significance for clinical evaluation of patients with COLD and for research into right ventricular contractility.