Protein arginine methyltransferase 1 (PRMT1), a type-I argininemethyltransferase, has been implicated in diverse cellularevents. We have focused on the role of PRMT1 in gliomagenesis.In this study, we showed that PRMT1 expression wasup-regulated in glioma tissues and cell lines compared withnormal brain tissues. The knock-down of PRMT1 resulted in anarrest in the G1-S phase of the cell cycle, proliferation inhibitionand apoptosis induction in four glioma cell lines(T98G, U87MG, U251, and A172). Moreover, an in vivo studyconfirmed that the tumor growth in nude mouse xenografts wassignificantly decreased in the RNAi-PRMT1 group. Additionally,we found that the level of the asymmetric dimethylatedmodification of H4R3, a substrate of PRMT1, was higher inglioma cells than in normal brain tissues and decreased afterPRMT1 knock-down. Our data suggest a potential role forPRMT1 as a novel biomarker of and therapeutic target ingliomas.