SUMMARYThe early recognition and prompt treatment of rejection may minimise damage to renal allografts. Preliminary studies showed whole blood effector cell function in a constant antibody-dependent cellular cytotoxicity (ADCC) assay system to be suppressed in recipients with stable renal function. To investigate the possible role of ADCC in the rejection process, serial estimates were performed in 29 consecutive recipients of cadaveric kidneys.The generation of ADCC, as measured in vitro, preceded the biochemical confirmation of an impending rejection episode by 3 to 5 days for 31 of 33 episodes experienced by 23 recipients. Statistical analysis (x2) demonstrated a highly significant correlation between ADCC generation as measured in vitro and subsequent episodes of graft rejection. In contrast, six recipients who did not experience rejection episodes during the first 3 months postgrafting showed no evidence of ADCC activity. Thus, ADCC may be used to identify rejection earlier than has previously been possible.