Seven patients received a renal allograft with negative standard and T-lymphocyte microlymphocytotoxicity cross-matches, but a positive B-lymphocyte cross-match using donor lymphocytes. In spite of this presensitisation, none underwent hyperacute rejection and all are functioning from one and a half to six months after transplantation. This procedure may help in the detection of false-positive cross-matches and possibly in detection of enhancing antibodies against a specific donor.