Objective.IDH1codon 132 mutation (mostly Arg132His) is frequently found in gliomas and is associated with longer survival. However, it is still unclear whetherIDH1mutation renders the cell more vulnerable to current treatment, radio- and chemotherapy.Materials and Methods. We transduced U87 with wild typeIDH1orIDH1R132Hexpressing lentivirus and analyzed the radiosensitivity (dose ranging 0 to 10 Gy) under normoxia (20% O2) and moderate hypoxia (1% O2).Results. We observed thatIDH1R132HU87 cells grow faster in hypoxia and were more sensitive to radiotherapy (in terms of cell mortality and colony formation assay) compared to nontransduced U87 andIDH1wtcells. This effect was not observed in normoxia.Conclusion. These data suggest thatIDH1R132Hmutation increases radiosensitivity in mild hypoxic conditions.