Isolated porcine small intestine submucosa has been used as a resorbable bio-scaffold for site-specific tissue remodeling. This study performed in swine evaluated the functional competency and remodeling characteristics of cardiac pulmonary leaflets constructed from porcine-derived small intestine submucosa.Four clinically normal swine were used for this study. Under general anesthesia and cardiopulmonary bypass, each swine had one pulmonary valve leaflet excised and replaced with a leaflet constructed from a single layer of porcine small intestine submucosa. The animals were sacrificed one each, at 56, 63, 88 and 111 days postoperatively. Histopathological evaluation was carried out to compare substitute leaflets with normal host valve leaflets, and valve functional competence was determined using echocardiography.Histopathological analysis of the substituted valve leaflet at the time of sacrifice revealed that, simultaneous with resorption of the submucosal matrix, progressive replacement with fibrous connective tissue and microvasculature similar to mature host tissue had occurred. Factor VIII staining demonstrated progression of endothelialization of all substitute leaflet surfaces with time. Normal valvular competence was noted immediately following surgery, and at the time of sacrifice.This study supports the hypothesis that single-layer porcine small intestine submucosa can be used to replace mature pulmonary valve leaflets. The implanted matrix is resorbed, and a leaflet with histologically identifiable features, normal functional competency and anatomic apposition to the host leaflets remains.