The present study reports on 15 transplanted patients with acute vascular rejection unresponsive to high-dose steroids, who underwent plasmapheresis treatment. Cyclophosphamide was combined with plasmapheresis in 11 patients in whom specific anti-HLA antibodies against the donor's mismatched antigens were detected. The treatment proved effective in removing the antibodies from circulation and in improving the graft function. Nine of these patients have a well-functioning graft 3 to 24 months after treatment. Plasmapheresis failed to reverse rejection in two out of the four patients where anti-HLA antibodies were not found, while the remainder have a satisfactory renal function after 18 and 32 months respectively. We conclude that in transplanted patients plasmapheresis associated with an appropriate immunosuppressive therapy may be of value in the treatment of acute vascular rejection that is unresponsive to high-dose steroids, particularly when specific anti-HLA antibodies are detected.