The relative merits of three methods of diaphragmatic hernia repair were evaluated in animals. Eighty Sprague-Dawley rats underwent laparotomy. The control group had an incision in the diaphragm with primary repair. The other three groups underwent partial resection of the left hemidiaphragm. The defects were repaired in 20 rats with lyophilized Dura, in 20 with polytetrafluoroethylene (PTFE) and in another 20 with absorbable serosa from a cow. Seventy-two animals survived the operation; they were followed up by electromyography (EMG) and post-mortem physical and histological examinations after 3 and 6 months. The EMG showed normal function for the absorbable material. Only scanty physiological waves were registered in the PTFE group. The examination for stretching and stress showed good results for all materials tested. The histological examinations amount to strong foreign body reactions with Dura and PTFE groups. The absorbable bovine serosa had vanished after 3 months postoperatively. It is concluded that bovine serosa can be recommended for diaphragmatic hernia.