The association of partial anomalous pulmonary venous connection with intact atrial septum and isolated severe nonrheumatic mitral regurgitation is rare, this combination of lesions having been reported on only one other occasion. Two such cases have been presented, with each patient having experienced an episode resembling subacute bacterial endocarditis. At operation, however, the mitral valve had a congenital cleft in one case and was normal in the other. One patient underwent mitral valvuloplasty and the second patient had mitral valve replacement. The diagnosis of associated partial anaomalous pulmonary venous connection was established at cardiac catheterization, and successful surgical correction was achieved in each case by diversion of the anamolaous pulmonary venous drainage to the left atrium via a pericardial tunnel through a surgically created atrial septal defect.