AbstractIDH mutational status is required for proper diagnosis according to the WHO criteria revised in 2016. The single nucleotide polymorphism (SNP) rs11554137 (IDH1^105GGT) at codon 105 of IDH1 has been reported in patients with several tumor types, including those with glioma. The aim of this study is to investigate the prevalence of IDH1^105GGT in a cohort of brain tumors, and its association with clinicopathologic features and IDH1 and IDH2 missense mutations. Exon 4 of IDH1 and IDH2 was analyzed in a series of brain tumors classified according to current WHO criteria. DNA from control individuals was analyzed to infer the prevalence of IDH1^105GGT in the reference population. Analysis was performed using next generation sequencing. IDH1^105GGT was three times more frequent in patients with tumors (44/293 cases, 15.0%) vs. population controls (6/109, 5.5%) (p = 0.0102). IDH1^105GGT was more frequent in grade III tumors (26.1%) compared to grade II (10.9%, p = 0.038) and grade IV tumors (13.7%, p = 0.041). IDH1 ^105GGT was more frequent in grade II and III tumors without an IDH tumor missense mutation (43.8%) than in those with (11.5%, p = 0.005). The IDH1^105GGT SNP likely represents an important genetic marker, worthy of additional investigation to better understand the clinical and biological features of IDH-WT infiltrating gliomas.