Acute ischaemia limited to the free wall of the right ventricle was produced by right coronary arterial ligation (RCAL) in 20 dogs. Contrast M-mode and cross-sectional echocardiography was performed in 7 cases to investigate the presence of tricuspid insufficiency. The haemodynamic findings obtained with an open pericardium at 15 to 30 min showed increases in right (1.2 +/- 0.5 to 2.7 +/- 0.7 mmHg, P less than 0.01) and left (5.0 +/- 0.8 to 6.6 +/- 0.9 mmHg, P less than 0.05) ventricular end-diastolic pressures, and decreases in heart rate (139 +/- 4.9 to 119 +/- 5.1 bpm, P less than 0.01), cardiac index (106 +/- 6.6 to 81 +/- 7.3 ml min-1 kg-1, P less than 0.01), stroke index (79 +/- 6 to 72 +/- 8 ml X 100 beat-1 kg-1, P less than 0.02), right (23.8 +/- 1.5 to 19.4 +/- 1.5 mmHg, P less than 0.01) and left (109 +/- 7.2 to 95 +/- 8.2 mmHg, P less than 0.05) ventricular systolic pressures and right ventricular stroke work index (18.3 +/- 2.4 to 11.4 +/- 1.8 g m kg-1, P less than 0.01). In 6 of 15 cases the 'y' descent became deeper than the 'x' descent in right atrial pressure (RAP). Tricuspid insufficiency grade I-II/IV was present in 3 of 7 cases, 2 of them with a 'y' greater than 'x' in RAP. Right ventricular mechanical alternans, probably secondary to a decrease in contractility, appeared in 10 of 20 cases after RCAL.(ABSTRACT TRUNCATED AT 250 WORDS)