Abstract: patients with acute nonlymphocytic leukemia were treated with intermediate dosesof Ara-c and CTX for intensive chemotherapy after lst complete remission. A rebound phenomenonof marrow blast cells was seen in 10 patients during therapy.The range of blast cells was 7-38%, and it returned to≤5% after a mean duration of 17 days. Serum ferritin, GM-CFUand L-CFU were assayed before intensive chemotherapy in these 10 patients,and the prognosticsignificance of this rebound phenomenon was discussed.