ObjectiveTo quantitate expression of miR21 in rectal cancer of different tumor stages and discuss their significances. MethodThe expression of miR21 was detected and quantitated in the rectal cancer tissues and corresponding adjacent normal tissues of 40 patients with rectal cancer in this hospital from August 2012 to October 2012 by Taq Man microRNA assay. ResultsThe significant overexpression of miR21 was observed in the rectal cancer tissues (4.122±1.973 versus 1.825±0.661, P=0.000)as compared with the corresponding adjacent normal tissues. The expressions of miR21 in the rectal cancer tissues of N1-N2 and Dukes C-D stages were significantly higher than those in the rectal cancer tissues of N0(4.852±2.344 versus 3.391±1.171, P=0.019)and Dukes A-B stage(4.787±2.304 versus 3.386±1.203, P=0.021). From N0 to N2 stage, the expression of miR21 increased progressively in the rectal cancer, and the expression in the rectal cancer tissues of N2 stage was significantly higher than that in the N0 stage(5.556±1.500 versus 3.391±1.171, P=0.010). And receiver operating characteristics curve analysis showed that miR21 could discriminate N 0 stage from N1-N2 stage with a 0.698 area under curve(AUC), 50.0% sensitivity and 90.0% specificity, Dukes C-D stage from A-B stage with a 0.689 AUC, 42.9% sensitivity and 94.7% specificity. ConclusionmiR21 appears to have a potential correlation with N and Dukes stages of rectal cancer, which cautiously and optimistically suggests that it could be a potential novel biomarker for predicting tumor stage preoperatively.