Publisher Summary Leukemia is not a condition that kills by over production of cells, which causes occlusion or compression of vital organs, but in which death and morbidity from hemorrhage or infection are the results of a severe inadequacy of normal blood cells. This approach has led to an increase in the frequency of remission, in remission duration, and in the apparent cure of some patients. Recent approaches in treatment of leukemia include use of “differentiation-inducing agents.” Moreover, it was possible to find predictive value in the in vitro differentiation studies. None of the patients had aggravation of hemorrhagic manifestation or appearance of coagulation parameter abnormalities suggesting disseminated intravascular coagulation (DIC) during the course of retinoic acid (RA) treatment. From the data obtained from both the clinical survey and the cytogenetic studies showing the persistence of abnormal clones (unpublished data), it is possible to suggest that intensive chemotherapy after complete remission (CR) may be beneficial. Based on these observations, we conclude that all Trans RA are an effective agent for obtaining CR in APL. A method of maintaining and prolonging the duration of CR, however, requires further study.