Objective To observe the characteristics of folate binding proteins (FBP) in myelodysplastic syndromes (MDS) and leukemia and to study the clinical significance of reduced folate carrier (RFC) present in MDS and its relationship with multidrug resistance (MDR).Methods The features of FBP on bone marrow cells were analyzed using radiolabeled 3 H-folic acid (3 H-FA) binding membrane proteins and SDS-polyacrylamide gel electrophoresis (SDS-PAGE). In the same time, P-glucoprotein and mRNA of MDR gene were detected using immunocytochemistry and reverse transcription ploymerase chain reaction (RT-PCR) respectively in patients with MDS and leukemia.Results Two kinds of FBP, folate receptor (FR) and reduced folate carrier (RFC), were found on the leukemic cells. The same results were presented on mononuclear cells of bone marrow in 5 out of 14 MDS patients, and MDR positive was seen in 4 patiens of them. In normal control and other 9 cases of MDS FRs were only found on the mononuclear cells of bone marrow.Conclusion Reduced folate carrier, which is present in the leukemic cell, is a product of neoplastic cell. It might reveal preleukmic state and have the same significance with MDR that RFC is found in MDS patients.