Only a few indications exist for diaphragm replacement: aplasias, tumours and accidents. The defect may be so extensive that it is impossible to close the gap. Allogenic and autologous materials are proposed for replacement of the diaphragm. The disadvantages of allogenic materials are recurrence rates of up to 20% and a high rate of malalignment of thoracic muscles and bones; the implication of autologous materials requires a longer operation time and no long-term results exist. To avoid these disadvantages, we have tested a material from bovine serosa, which is absorbable for a short time, for diaphragm replacement.The merits of four methods of diaphragmatic hernia repair were evaluated in animals. One hundred Sprague-Dawley rats underwent laparotomy. The control group had an incision in the diaphragm with primary repair. The other four groups underwent partial resection of the left hemidiaphragm. The defects were repaired in 20 rats with lyophilized dura, in 20 with polytetrafluoroethylene (PTFE), in 20 with autologous transversus muscle and in another 20 with absorbable serosa from a cow. The animals were followed up by electromyography (EMG) and post-mortem physical and histological examinations after 3 and 6 months.Eighty-nine animals survived the operations. The EMG showed normal function for the absorbable material and the transversus muscle. Only scanty physiological waves were recorded in the PTFE group. The examination for stretching and stress showed good results for all materials tested. The histological examinations showed strong foreign body reactions in the dura and PTFE groups. The absorbable bovine serosa had vanished after 3 months postoperatively.We conclude that bovine serosa can be recommended for the treatment of diaphragmatic defects.