Among 73 patients who were admitted to our hospital between 1972 and 1983, 9 died before starting chemotherapy, 29 achieved complete remission (CR) with an initial regimen of induction chemotherapy, while the remaining 35 patients failed to achieve CR with this initial regimen. Patients with high initial WBC counts (greater than 100,000/cmm), old age, temperature (greater than 38 degrees C) and antecedent hematological disorders, were more prone to failure of remission induction therapy. Comparing CR patients and non-CR patients, there seemed to be no difference in sex distribution, initial platelet counts, initial LDH, percentage of blasts in the blood and bone marrow, the incidence of DIC and the regimen used for remission induction. According to Preisler's criteria, remission induction failure cases were further subdivided into various types and the numbers of each type were as follows: Type I (absolute drug resistance) 1, Type II (relative drug resistance) 16, Type III (regeneration failure) 0, Type IV (hypoplastic death) 6 and Type V (early death) 11. Among 18 M1 cases, 8 were Type II or Type V. Four out of 7 M2 cases belonged to Type II and all 3 M3 cases were Type V. Six out of the 35 remission induction failure patients entered CR with the 2nd chemotherapy regimen and 19 patients died during induction treatment with the initial induction regimen. Causes of death were infection (5 cases), bleeding (6 cases), infection and bleeding (3 cases) and organ failure (5 cases).