OBJECTIVE: To conduct a test of noninferiority for CardioCel (Admedus, Brisbane, Australia), a chemically engineered bovine pericardium over autologous pericardium treated intraoperatively with glutaraldehyde in a chronic juvenile sheep model of pulmonary valve (PV) and mitral valve (MV) reconstruction. METHODS: We replaced the posterior leaflet of the MV and of 1 PV cusp with patches in ewes aged 10 months. There were 2 groups: CardioCel (n = 6) and control (n = 4). All valves were competent. Echocardiography was performed before euthanasia. The collected data were function, macroscopy, histology, and calcium contents. The primary end points were thickening and calcium content. RESULTS: All animals survived until sacrifice after 7 months. The valves had normal echo. The macroscopic aspect of the valves was excellent. Examination of the slides for both groups revealed a continuous endothelium on both sides of the patch and a layer of new collagen developed on both sides between patch and endothelium and interstitial cells and smooth muscle cell in these layers. The patch had not thickened but the 2 layers of new collagen for the PV showed a median thickening of 37% in the CardioCel group and 111% in the control group (P = .01), and for the MV a thickening of 108% and 251%, respectively, was seen (P = .01). The median calcium content in the PV was 0.24 μg/mg (range, 0.19-0.30) in the CardioCel group versus 0.34 μg/mg (range, 0.24-0.62) in controls (P = .20). In the MV it was 0.46 μg/mg (range, 0.30-1.0) in the CardioCel group and 0.47 μg/mg (range, 0.29-1.9) in controls (P = 1.0). CONCLUSIONS: In this growing lamb model the CardioCel patch allowed accurate valve repair at both systemic and pulmonary pressure. The mechanical properties of CardioCel after 7 months were preserved with a more controlled healing than the treated autologous pericardium and without calcification.