Total body irradiation (TBI) prior to bone marrow transplantation (BMT) is applied for treatment of 230 patients in the period 1975-1988. The clinical results of 169 patients treated by four different TBI dosage and treatment techniques are analysed. The risk of leukemic relapse is low after fractionated TBI (9%) as well as after single dose TBI (14%). The lowest frequency of interstitial pneumonitis (21%) occurred when the patient translation technique was used for fractionated homogeneous pa/ap TBI with 10 Gy (8 Gy lung dose) in 4 fractions in 4 days. Prophylaxis of GVHD and the modus of protective environment were two other factors which influence the risk of IP.