Objective To investigate the diagnosis performance of arterialspin labeling (ASL)in distinguishing pseudoprogression from recurrence in postoperation chemoradiotherapy patients with high-grade glioma. Methods 2D pASL was performed using a 3.0 Tesla scanner in 32 patients with high-grade glioma, who received previously resection and chemoradiotherapy, and newly developed abnormal contrast-enhanced lesions were noted at rountine following-up MRI. These patients were classified into a pseudoprogression group (n=7) and glioma recurrence group (n=25) based on subsequent pathologic analysis or clinical–radiological follow-up. Lesion perfusion parameter values -rCBF was compared between the two groups using Wilcocon rank sum test. The diagnosis performance of rCBF in distiguishing pseudoprogression from recurrence were assessed receiptor operation characteristic (ROC) curve. Results For the contrast-enhanced lesions, the rCBF in the pseudoprogression group was significantly lower than that in the glioma recurrence group [(1.45±0.25) vs (3.16±0.14) Z=-3.739,P=0.000]. The area under the ROC curve was 0.765（95% confidence interval:0.597-0.932) with a sensitivity of 0.647 and a specificity of 0.733for rCBF in diagnosis of pseudoprogression. Conclusion ASL is helpful in differentiating pseudoprogression from recurrence in high grade giloma patients with newly development enhanced lesions during routine following-up MRI after

therapy.