Chemotherapy remains a major route of intervention in hematological malignancies. However, a key issue in the treatment of hematological malignancies is the development of multidrug resistance (MDR) to chemotherapeutic drugs. Several mechanisms may account for this phenomenon, including biochemical mechanisms, such as the overexpression of resistance-conferring proteins and physiological mechanisms involving the hematopoietic microenvironment. In this article the pathomechanism, diagnostic approach, interpretation of results from clinical samples and correlations with hemopoietic microenvironment were briefly reviewed. The aspects of development and problems in MDR study as well as detection methods for MDR were also discussed.