Human malignant gliomas are highly lethal neoplasms. Postoperative involved-field radiotherapy is one of the most important therapeutic measures. Most relapses originate from the close vicinity of the irradiated target field. Here, we report that subsequent doses (2~8Gy) of irradiation inhibit the migration of human malignant glioma primary culture cells. The effects of radiation on directional migration in monolayer cultures were investigated on two types of malignant glioma primary culture cells. Simple scratch technique was employed to evaluate the effect of irradiation on migration of the culture cells. The Gamma Unit was the radiation source. The number of cells migrating across the wound edge and the maximum distance migrated were determined in each field and averaged for each injury. All experiments were repeated thrice. The number of migrating cells was significantly reduced after irradiation with 8 Gy in both of glioblastoma and anaplastic oligodendroglioma primary cultures, but these changes did not show a dose-dependent reduction of directional migration. Primary cultures of anaplastic oligodendroglioma showed a decrease in the maximum-migrated distance with a dose-dependent inhibition, but glioblastoma cells did not. Radiation effect on the migration was significantly inhibited in anaplastic ologodendroglioma cells rather than in glioblastoma cells. This preliminary study showed that irradiation could reduce migration ability of primary culture cells originated from the malignant gliomas. Further studies may provide fundamental knowledge on the effect of ionizing radiation upon the migration process of gliomas.