Repair of congenital right ventricular outflow tract obstruction often requires reconstruction with a transannular patch to alleviate pulmonary stenosis. Post repair pulmonary insufficiency with right ventricular dilatation and volume overload may result and lead to acute or progressive right heart failure. The use of a monocusp valve has been proposed as a means to prevent this problem. Fresh pericardium is well known to fail clinically, leading to pulmonary insufficiency limiting mid- and long-term results. In a chronic dog model (147 +/- 34 days), three valve types were evaluated: 1) polytetrafluoroethylene (PTFE; n = 9), 2) fresh pericardium (PERI; n = 6), and glutaraldehyde fixed pericardium (GLU; n = 6). Hemodynamics, angiography, and echocardiography were performed at implantation and sacrifice. Gross and microscopic pathology were evaluated. No significant differences were found among the three groups with regard to stenosis as evaluated by echocardiography, measured right ventricular wall thickness, and hemodynamic pressure gradients across the valve. By echocardiography, both PTFE (1 of 9) and GLU (0 of 6) showed less regurgitation than PERI (5 of 6) (p < 0.05). This was confirmed by angiography. PTFE showed less neo-intimal hyperplasia, less thrombus formation, and less calcification than GLU or PERI (p = NS). The PTFE monocusp developed no prohibitive gradients, no early pathologic deterioration, and maintained competence compared with the GLU and PERI groups. Although continued investigation of long-term durability and competence of the PTFE monocusp valve is warranted, both PTFE and GLU values seem to demonstrate less regurgitation than the PERI monocusp valve in an adult dog model of right ventricular outflow tract reconstruction.