One recent Korean prospective cohort study showed the potential survival benefit and safety of concurrent chemoradiotherapy with temozolomide followed by adjuvant temozolomide for WHO grade 3 gliomas. In this study, however, the role of molecular markers such as codeletion of chromosome 1p/19q and MGMT methylation could not be determined because of small number of patients available. These results prompted this Korean group to project a randomized phase 2 screening trial examining the efficacy of concurrent chemoradiotherapy with temozolomide followed by adjuvant temozolomide for WHO grade 3 gliomas without codeletion of chromosome 1p/19q. The basic concept of the present clinical trial is "a subgroup with expected worse prognosis according to the status of chromosome 1p/19q, i.e. one without codeletion of chromosome 1p/19q is to be managed more aggressively", to investigate the role of temozolomide. An aggressive therapy (surgery + concurrent chemoradiotherapy with temozolomide followed by adjuvant temozolomide) will be compared to the conventional arm (surgery + radiotherapy only) in terms of its efficacy and safety for WHO grade 3 gliomas without chromosome 1p/19q codeletion. The prognostic significance of methylation status of MGMT and IDH1 mutation as molecular markers will be also assessed in each arm as key secondary analysis. Until now, there have been no such trials examining the efficacy and safety of temozolomide for WHO grade 3 gliomas based on prospective molecular stratification.