From March 1982 to December 1986, 32 patients with standard risk leukaemia were conditioned for allogeneic bone marrow transplantation (BMT) with low dose fractionated total body irradiation (TBI) after infusion of alkylating agents. This series includes six children and 26 adults. Minimal follow-up was 24 months. The total dose of 11 Gy, given in 5 daily fractions of 2.20 Gy, was given in the lateral position, following chemotherapy with either melphalan or cyclophosphamide. Lungs were shielded for 2 out of the 5 fractions. All patients had in vivo dosimetry. The death rate is 25% without relapse or rejection. Disease-free survival is 73% at 5 years. Toxic deaths are detailed: 2 from sepsis and veino-occlusive disease of the liver, 3 from severe graft versus host disease (GVHD), 2 from GVHD associated with virus pneumonitis and one from HIV infection. Fractionated low dose rate TBI is discussed regarding its decreased toxicity and its efficiency for disease control.