The paper reviews current data on the use of imatinib in acute lymphoid leukemia. A brief description of classification of acute lymphoid leukemia and the therapeutic developments of the last 30 years are presented with particular emphasis on the clinical and biological features of Philadelphia positive acute lymphoid leukemia. The main therapeutic principles of acute lymphoid leukemia and the role of minimal residual disease in therapeutic indications are summarized. In Philadelphia positive acute lymphoid leukemia, in addition to chemotherapy and bone marrow transplantation, the tyrosine kinase inhibitor imatinib mesylate has been increasingly administered. The results of major clinical studies are presented along with the author's own clinical experience. Based on the above considerations the current indications of imatinib treatment in Philadelphia positive acute lymphoid leukemia can be summarized as follows: a) during the induction phase along with chemotherapy; b) alternating with cycles of consolidation or maintenance treatment; c) before stem cell transplantation to eradicate minimal residual disease; d) in relapsed or refractory cases; e) after stem cell transplantation for the treatment of minimal residual disease and/or relapse, alone or in combination with donor lymphocyte immunotherapy.