The objective of this study is to investigate the expression and significance of isocitrate dehydrogenase 1 (IDH1) mutation in different subtypes of human gliomas. Direct DNA sequencing, western blot, and immunohistochemistry were used to detect IDH1 mutation and IDH1 gene expression levels in 97 cases of glioma and 9 cases of other CNS tumors. IDH1 mutation was heterozygous, with wild-type arginine 132 replaced by histidine (R132H). Expression in different glioma subtypes was (1) 0 out if 5 in pilocytic astrocytoma; (2) 15 out of 22 in diffuse astrocytoma, 6 out of 9 in oligodendroglioma, 4 out of 6 in oligoastrocytoma, and 0 out of 4 in ependymoma; (3) 11 out of 19 in anaplastic astrocytoma, 4 out of 7 in anaplastic oligodendroglioma, 3 out of 4 in anaplastic oligoastrocytoma, and 0 out of 3 in anaplastic ependymoma; and (4) 1 out of 6 in primary glioblastoma, 8 out of 10 in secondary glioblastoma, and 0 out of 2 in medulloblastoma. IDH1 mutation is a somatic mutation that is found only in some glioma subtypes. It can be used as a molecular marker for glioma subtypes. For example, it can be used to distinguish primary glioblastoma from secondary glioblastoma, combining TP53 mutation and loss of heterozygosity involving 1p/19q. It can also be used as a marker for some gliomas. For example, it can be used to distinguish pilocytic astrocytoma from diffuse astrocytoma, combining detected BRAF proto-oncogene mutations.