This experimental study summarizes our experience with the use of a new polytetrafluoroethylene surgical membrane as a pericardial substitute in 24 dogs. Group I consists of 10 dogs who underwent simple pericardial closure with this membrane, and in Group II, 14 dogs had pericardial closure with this membrane after cardiac procedures. There were three early deaths. Two dogs that had undergone an associated right heart procedure developed endocarditis at 4 and 7 months, respectively. Postmortem examinations were performed in all 21 surviving dogs. The pericardial membranes were found to be acellular and to have maintained their initial characteristics. The epicardium was normal and the coronary arteries easily visible. Seven of the eight 0.2 mm thick membranes caused filmy pericardial adhesions. None of the 0.1 mm thick membranes formed adhesions or had any structural change. We conclude that this new 0.1 mm thick polytetrafluoroethylene surgical membrane should be clinically tested to see if it will reduce or eliminate pericardial adhesions and facilitate cardiac reoperation.