Purpose To study HSV reactivation and recurrent disease after corneal transplantation in rats.Methods Female PVG rats were inoculated on the cornea with HSV-1 McKrae. At least 4 weeks after inoculation, they received either allogeneic (DA or LEW) or syngeneic corneal grafts and were examined for signs of recurrent HSV disease for up to 30 days.Results All allografts were rejected. Virus was shed in the tear film of 4 rats (11%) receiving allografts and 7 rats (13%) receiving syngeneic grafts. This was comparable to that after UV-irradiation of the cornea, a known stimulus of recurrent disease. Characteristic epithelial lesions were seen on the recipient cornea of 3 animals. One syngeneic graft became completely opaque. Neither removal of sutures nor rejection provoked recurrent disease. Histological examination of 4 eyes that shed virus revealed HSV antigens in all at the graft host junction. HSV-expressing cells were numerous in the stroma and extended to the endothelium. Infiltrating cells in diseased areas were mainly HIS48 + granulocytes and many expressed HSV antigens.Conclusions Surgical trauma appears to be the most potent stimulus of recurrent disease after transplantation. Virus occasionally recurs in the recipient epithelium, but does not penetrate the basement membrane to the stroma. The graft-host junction appears to be a 'weak spot' where antigen readily reaches the stroma, perhaps from nerve endings severed in the operation. Infiltrating cells then act as a conduit to the endothelium, which may become infected and prejudice the graft.