Using a cDNA microarray 12 differentially expressed genes were identified in a multidrug resistant (MDR) cell line K562/A02. The differential expression of sorcin, which was one of the 12 genes, has been confirmed by Northern blot. To determine the clinical role of sorcin, we have measured its expression in leukemic blast cells of 65 acute myeloid leukemia (AML) patients by reverse transcriptase polymerase chain reaction (RT-PCR). Sorcin overexpression in AML patients was associated with poor clinical outcomes, the complete remission (CR) rate in sorcin- cases was significantly higher than that of sorcin+ cases (P<0.001). Furthermore, sorcin expression in AML patients was positively correlated with mdr1 expression (r=0.841, P<0.001). Combination of sorcin and mdr1 was related to clinical outcome too, cases with sorcin-/mdr1- had best response to induction chemotherapy. Our results indicated that sorcin might be one of the factors that contributes to drug resistance of AML patients.