Current classification of acute leukemia is based on morphology, immunophenotyping, cytogenetic and molecular abnormalities of leukemic cells. All these techniques have a diagnostic and prognostic value. Molecular abnormalities in many cases suggest the pathogenesis of acute leukemia, but also point to the key site of genetic abnormalities that may be targeted with the therapy. Treatment approach in acute leukemia is still chemotherapy. The probability of long-term disease-free survival after intensive chemotherapy for younger patients with acute lymphoblastic leukemia and acute myeloid leukemia is 30%-40% and 40%-50%, respectively. Allogeneic stem cell transplantation is associated with better disease-free survival compared to other cytotoxic regimens. In recent years, targeted therapy seems to improve the chemotherapy outcome. This therapy targets only leukemic cells while sparing normal cells. Immunotherapy, differential agents and especially drugs acting on the key molecular abnormalities are currently being used together with chemotherapy as a treatment approach for acute leukemia. It is expected that techniques such as gene expression profiling will identify genetic abnormalities and their proteins as a targeted site for new drugs. This might increase the efficacy of leukemia treatment and control.