This chapter discusses the treatment of acute and chronic leukemia during pregnancy. Leukemia occurs very rarely during pregnancy. The majority of cases are acute leukemia; of which two-thirds are myeloblastic (AML) and one-third are lymphoblastic (ALL). Chronic myeloid leukemia (CML) is found in less than 10% of leukemia cases during pregnancy, and chronic lymphocytic leukemia (CLL) is extremely rare. The treatment of CML has evolved dramatically since the introduction of tyrosine kinase inhibitors (TKI). There are several options for the treatment of CLL. When treatment is indicated, cytoreduction may be accomplished mechanically with leukapheresis. The most popular drugs are: chlorambucil, which is contra-indicated during the first trimester of pregnancy because of its teratogenicity; and fludarabine, an anti-metabolite. Corticosteroids may be used for the treatment of autoimmune complications, as in nonpregnant patients. Hairy cell leukemia is very rare during pregnancy. Interferon alpha was historically used in the treatment of this disease.