This study was performed to assess a new vascular stent graft as an expandable valved conduit for right ventricular outflow tract (RVOT) reconstruction in sheep. Conduits were constructed by sewing an 18-mm valved conduit inside a stent. Crimped to 16 mm, they were implanted either under or without extracorporeal circulation in seven (group A) and in five (group B) sheep, respectively. Six weeks and 3 mo after their insertion, conduits were dilated intraluminally. A valved stent was implanted percutaneously into conduits before they were killed. Two animals from group A recovered normally, whereas five animals had a complicated postoperative course. In group B, one died acutely due to kinking of the conduit. Balloon dilatations were performed in all surviving animals. First dilatations had a slight impact on valvular function in all animals but one, whereas second dilatations led to significant PR in all. Transcatheter valve implantation was performed successfully. When animals were killed, no bleeding was found around the surgically implanted device. In conclusion, we designed a biologic valved conduit for RVOT reconstruction that can be dilated sequentially to follow animal growth. This new device can have tremendous applications in children with congenital heart diseases involving the RVOT.