Cadaveric renal transplants were performed despite a positive conventional crossmatch (usually intermediate positive) resulting from donor-specific B cell lymphocytotoxins (both IgG and IgM) or IgM cold-reactive T cell lymphocytotoxins. Graft survival at 2 months was 72% in the 14 patients with B cell-specific antibodies and 71% in the 7 recipients with T cell antibodies. No correlation was observed between graft rejection and warm (mainly IgG) or cold (IgM) B cell-specific antibodies. These results indicate that not all positive crossmatches are a contraindication to transplantation. Attempts should be made to study the nature of the lymphocytotoxins before withholding the allograft from the recipient.