A group of 50 patients with chronic myelocytic leukaemia in blastic crisis were treated with different chemotherapeutic regimens. A total of 19 remissions (6 CR + 13 PR) were achieved with an overall and complete response rate of 38% and 12% respectively. Of the 4 patients presenting with a lymphoblast-like appearance of the blasts, the 3 treated with the combination of vincristine and prednisone all achieved remission (2 CR + 1 PR). Duration of survival was significantly longer in responding patients (median 11.5 versus 4.5 months). Either more effective therapeutic regimens or prevention by aggressively approaching the chronic phase are to be sought in order to improve the prognosis of blastic crisis of CML.