Abstract： Objective To investigate the predictive value of ADC value in grading of neuroepithelial tumors. Methods The clinical data and images of 70 patients with neuroepithelial tumors pathologically proven were collected and analyzed restrospectively. All the patients were classified into low(WHOⅠ or Ⅱ)and high(WHO Ⅲ or Ⅳ)grade groups which included 40 and 30 cases respectively accroding to the 2007 WHO classification of tumours of the central nervous system. All the patients underwent plain and contrast-enhanced MR scan and DWI before surgery. The minimum ADC(MinADC)value was measured postoperatively on ADC maps. The Ki-67 labeling index(Ki-67 LI)of tumor tissue was determined by immunohistochemistry.MinADC values for two groups were analyzed using student t test, while the age and Ki-67 LI for the two groups was analyzed using Mann-Whitney test(P＜0.05 considered to be significant＝.Also the MinADC valHe and Ki-67 LI were analyzed with Pearson correlation. The receiver operating characteristic analysis was used for evaluation for grading neuroepithelial tumors of the patients using MinADC. Results The mean MinADC value[(1.08±0.31)×10~(-3) mm~2/s]of the low grade group was significantly higher than that[(0.74±0.18)×10~(-3) mm~2/s]of the high grade group(t=5.42,P＜0.05＝,and the Ki-67 LI of the low grade group[0-50%,median 4%]was significantly lower than that[0-75%,median 25%]of the high grade group(U=325.50,P＜0.05＝.There was a negative correlation between MinADC value and Ki-67 LI(r=-0.30,P＜0.05＝.The area under the ROC curve was 0.85,and the cutoff MinADC value of 0.86×10~(-3) mm~2/s for the differentiation between high and low grade neuroepithelial tumors provided the best combination of sensitivity(90.0%)and specificity(77.5%)(receiver operatingcharacteristic analysis).Conclusion MinADC value is helpful for prediction of neuroepithelial tumor grade.