This paper compares the immunomagnetic (IM) and the KN lymphocytotoxic cross-matching techniques. Only sera from patients with panel reactive antibodies and spleen cells from cadaveric donors were used. A panel study involving 60 combinations revealed 11 (18%) discrepancies. Four T-cell cross-matches were KN negative while IM positive. Inversely, six T-cell cross-matches were IM negative while KN positive (two) or doubtfully positive (four). Regarding HLA class II antibodies, one combination was found IM positive but KN negative. Out of 106 cadaveric renal allograft transplantations performed during 1987 with assistance from our laboratory, IM cross-matching was retrospectively performed on 33 KN T-cell cross-match negative donor-recipient pairs: two combinations were found T-cell cross-match positive. The corresponding allografts were not lost owing to hyperacute rejection involving performed antibodies. We recommend the IM technique for HLA typing, but more experience needs to be gained before we can recommend the technique for routine cross-matching prior to transplantation.