A randomized crossover protocol was used to compare conventional mechanical ventilation (CMV) and high-frequency ventilation (HFV) in mongrel dogs experiencing right ventricular dysfunction after right ventriculotomy. When inspired oxygen, pH, Pco2, core temperature, and preload were held constant, cardiac output increased significantly (p < .05) from 1.16 ± 0.24 to 1.38 ± 0.25 L/min and pulmonary vascular resistance decreased significantly (p < .05) from 734 ± 257 to 554 ± 169 dyne sec/cm5 during HFV relative to CMV. We also noted a significant (p < .05) increase in mean arterial pressure from 116 ± 27 to 124 ± 23 mm Hg and a significant (p < .05) increase in left ventricular stroke work from 10.2 ± 3.5 to 12.3 ± 2.6 gm during HFV. During the inspiratory phase of CMV there were increases in CVP, pulmonary artery pressure, and systemic arterial pressure, and decreases in pulmonary artery flow which did not occur during HFV. HFV may be preferable to CMV in the presence of right ventricular dysfunction.