A questionnaire survey, concerning the immunosuppressive treatment and criteria of diagnosis in acute rejection of renal allografts, was done at 22 institutes. In 15 institutes, 3 immunosuppressive agents were used. Those agents were as follows: prednisolone (Pr.) or methyl-prednisolone (M-Pr.), cyclosporin (CsA) and azathioprine (Az.) or mizoribine (Mz.) or anti-lymphocyte globulin (ALG). A combination of 4 drugs (Pr. or M-Pr. +CsA +Az. or Mz. +ALG) was used at 4 institutes and a combination of 2 drugs (Pr. or M-Pr. +CsA) at the remaining 3 institutes. Acute rejection episodes were diagnosed by conventional criteria in all institutes. Conventional criteria were as follows: physical findings, rising serum creatinine, response to pulse therapy, rising urinary FDP, decreasing urinary Na/K ratio and radionuclide findings. In our cases, there was no significant difference between the number of acute rejection episodes by the 25 patients who underwent conventional immunosuppressive therapy (C group:M-Pr.+Az.) and the 25 patients with triple immunosuppressive therapy (T group: M-Pr. +CsA+Az.). Conventional methods were sufficient in most cases of the T as well as C group to diagnose acute rejection episodes.