The purpose of this study was to determine whether the crimping of arterial prostheses affected their healing. In ten dogs, 6 mm knitted Dacron grafts were implanted in the infrarenal aortas; 6 grafts were crimped, 4 uncrimped. Each was seeded with venous endothelium to produce a cellular lining. The grafts were removed a month after implantation and compared by light microscopy as to the (1) thickness of the inner lining, (2) completeness of endothelial healing, and (3) patterns of vasa vasorum. (1) and (3) were assessed using H & E sections and (2) by AgNO3 Häutchen preparations. The lining in uncrimped grafts was thinner and more uniform than in crimped grafts: 50.1 +/- 45.7 vs 263 +/- 183 mu, p < 0.001. While the completeness of healing was similar for both groups, 4 crimped grafts had unhealed areas in the centers of the crimps, corresponding to the thicker areas of the linings. In both kinds of grafts, vasa vasorum communicated with vascular channels parallel to the axis of flow and near the perigraft fat. In the uncrimped grafts, the smaller secondary vasa also were directed along the axis of flow, in contrast to crimped grafts in which they were circumferential to the graft and parallel to the crimps. In all instances vasa penetrated within 500 mu of the lumen. We conclude that crimping causes a change in the pattern of development of vasa vasorum in healing fabric grafts and a thicker inner lining associated with areas of delayed healing which may increase the risk of thrombosis.