Significant clinical responses obtained with interleukin 2 (IL-2) in solid tumors such as renal cell cancer and malignant melanoma prompted the use of this immunomodulatory drug to verify its activity in hematological malignancies. Several preclinical experiments showed an activity of IL-2 against leukemic cell lines in cultures, particularly in acute myeloid leukemia (AML), while only episodically a proliferative stimulus of IL-2 on the growth of leukemic blasts has been observed. Based on these preclinical studies, in the past five years several phase I-II clinical trials have verified IL-2 activity in AML in advanced phase, both in patients with active disease and in patients in further complete remission (CR). Data obtained are difficult to evaluate due to the low number and the heterogeneity of patients treated, but encouraging results have been reported in patients with "limited" disease (bone marrow blastosis < 30%), showing an antileukemic activity of IL-2 alone. Different international phase III trials are ongoing in AML patients in I CR after autologous bone marrow transplantation (Roussel-Uclaf, Romainville, France) and in II CR after conventional chemotherapy (Roche SpA, Milan, Italy) to verify the efficacy of IL-2 in reducing the risk of relapse and prolonging disease-free survival.