WHO2007 grading of diffuse gliomas in adults is well-established. However, IDH mutations make classification of gliomas according to the WHO2007 edition controversial. Here, we characterized IDH1R132H (mut) status in a cohort of 670 adult patients with different WHO2007 grades of diffuse glioma. Patient characteristics, clinical data and prognoses were obtained from medical records. Patients with IDH1R132H (mut) were younger and had better clinical outcomes than those without mutations. Differences in age among patients with astrocytomas of different WHO2007 grades were eliminated after patients were grouped based on IDH-1(R132H) status. IDH1R132H (mut) was present more often in patients with lower Ki-67 and MGMT protein levels and higher mutant p53 levels. Ki-67 was also strongly associated with WHO2007 grade independently of IDH-1(R132H mut) status. Moreover, patients with Ki-67< 30 survived longer than those with Ki-67 >= 30, regardless of IDH1R132H (mut) status. Patients in the IDH-1(R132H mut) group with lower MGMT protein levels also had better clinical outcomes than those in other groups. Our results indicate that to better treat gliomas, IDH mutation status should be included when determining WHO2007 grade in glioma patients.