During the past decades, monoclonal antibodies have been used as vehicles to deliver targeted therapy to sites of leukemic involvement. Anti-CD33 antibodies have been used alone-and more effectively, attached to chemotherapy agents or radioisotopes-to treat those with acute myeloid leukemia. Anti-CD45 antibodies have demonstrated an antileukemic effect when used either unconjugated or attached to radioactive iodine. Antibodies reactive with the myeloid antigen CD66 have been used to deliver targeted radiation to hematopoietic tissues in patients with advanced myeloid malignancies. Antibodies reactive with CD52 and CD20 antigens have been studied for the management of B-cell leukemia. This article reviews the most current clinical trials using monoclonal antibodies in the management of leukemia.