Aortic root enlargement with a patch is sometimes indicated either to prevent aortic homograft valve distortion during implantation or to facilitate easy, tension-free closure of the aortotomy. Patches made of prosthetic material have been widely used for this purpose. The use of autogenous pericardium has recently been reported. Although dura mater has been shown to have great strength, low antigenicity, athrombogenicity, easy availability in large sizes and rapid bonding to most tissues, its use for patch enlargement of the aortic root has not been previously documented. From 1979 to 1983, 38 patients had dura mater aortic root gussets placed during aortic valve replacement at the Southampton General Hospital. In all cases, the patches were placed to facilitate aortic closure, or to prevent homograft valve distortion by enlarging the non-coronary sinus. Aortic homografts were implanted in 11 patients, Carpentier Edwards' Xenograft valves in 16, Björk-Shiley valves in 8 and Wessex Xenografts in 3 patients. All the patients survived and in a mean follow-up of 30 +/- 12.8 months (range 3 to 48 months) there has been no clinical evidence of patch failure due to leakage, rupture or aneurysm formation. These results suggest that glycerol-preserved dura mater is a satisfactory patch material for aortic root enlargement during aortic valve replacement.