[en] BMT in Japan was started in 1975. From 1981 Japan BMT study group was organized by the grant of ministry of health and welfare Japan. A rapid increase of number of BMT parallel to the improvement of results was observed in the 489 patients by the registry of this group. The major causes of failure of BMT were interstitial pneumonitis (IP), relapse of leukemia, infection, and graft versus host disease (GVHD). The incidence of IP decreased very rapidly by fractionation of total body irradiation and anti-cytomegalovirus (CMV) antibody negative platelet transfusion. Prophylactic administration of anti-CMV immunoglobulin produced also significant reduction of IP. In the double blind controled study oral administration of aciclovir revealed significant reduction of herpes stomatitis, followed by the reduction of other infections including sepsis. For the decontamination of bioclean room we have developed ozone decontamination, which revealed to be very effective for fungus. Colony stimulating factor was found to shorten the period of granulocytopenia. The patients with GVHD showed lower incidence of relapse of leukemia than those without GVHD. In the patients who received BMT during their first remission of ALL. Long survival rate was 63 %, for ANLL in the first remission, 64 % and for CML in the chronic phase, 40 %. Out of the first 20 BMT patients of the center for adult diseases Osaka, only three are living now, while out of the next 25 patients 22 are living disease free. Major items of modification of BMT procedures between those two groups were cyclosporine A, colony stimulating factor, fractionated TBI, CMV-negative platelet donar, BMT in first remission for acute leukemia or chronic phase in CML. BMT seemed to be a very reliable and promising treatment of leukemia with a very high possibility of complete cure. (author)