The immunological reactivity of 20 consecutive renal allotransplanted patients against donor lymphocytes were followed from the day of transplantation and subsequently twice weekly until dismissal or graftectomy. The investigations concerned Complement Dependent Cytotoxic (CDC) antibodies, Antibody Dependent Cell-Mediated Cytotoxicity (ADCC) and Cell-Mediated Lymphocytotoxicity (CML). Five patterns of immunological reactivity were observed parallelling the clinical courses. A specifically positive CML test was highly but not absolutely correlated to clinical graftrejection. Graftrejection was in general not preceeded by positive CML. The patterns of CDC and ADCC reactivity in relation to graftrejection were not evident.