Human leukemia results from multiple mutations that lead to abnormalities in the expressions and functions of genes that maintain the delicate balance between proliferation, differentiation and apoptosis. Continued research on the molecular aspects of leukemia cells has resulted in the developments of several potentially useful therapeutic agents. Discovery of new cellular and/or molecular pathways enabling innate or acquired resistance of cancers to current chemotherapeutics to be overcome is therefore of crucial importance if one wants to efficiently combat those cancers associated with dismal prognoses. In this concern, natural compounds are regarded as new chemical entities for the development of drugs against various pharmacological targets, including cancer, and, above all, leukemia.