Assist devices have become available for the treatment of right ventricular (RV) failure. The present study assesses the efficacy of pulmonary artery balloon counterpulsation (PABC) in restoring RV output to normal levels. In a porcine model of RV failure during left heart bypass, PABC restored RV output to normal, provided that the RV output was not depressed to less than 50% of baseline values. When RV failure was more severe, PABC was not effective in restoring RV output to base line. This study suggests that a rational approach should be developed for the use of right heart assist devices. In moderately severe RV failure, PABC may be successful in restoring cardiac output to normal. However, in extreme failure a right heart bypass is necessary.