Of 82 patients with acute promyelocytic leukemia (APL) who were treated with all-trans retinoic acid (ATRA), 35 developed leukocytosis and 22 fatal side-effects(15 with retinoic acid syndrome and 7 intracranial bleeding). There was a high mortality in the patient with fatal side-effects. The relationship between leukocytosis and fatal side-effects was analyzed and the effect of therapeutic interventions on the development and prognosis of the fatal side-effects was investigated. The results showed that leukocytosis was a risk factor of the development of fatal side-effects in APL treated with ATRA. ATRA combined with small dose of harringtonin in treating APL can reduce the incidence of intracranial bleeding resulted from leukocytosis and corticosteroid can decrease the mortality of retinoic acid syndrome.