In leukemias and malignant tumors the balance between apoptosis and cell proliferation is dysregulated. This review deals with the apoptosis in acute leukemia. There are several publications about the molecular basis of decreased apoptosis in acute lymphoid leukemia (ALL) and AML. However, there have been contradictory results. Different results are published about the correlation of the spontaneous and induced apoptosis in leukemia with prognosis. The potential causes of these contradictions are discussed.