Somatic mutations of isocitrate dehydrogenase 1 and 2 (IDH1/2) are strongly associated with pathological subtypes, genetic profiles, and clinical features in gliomas. The IDH1/2 status is currently regarded as one of the most important molecular markers in gliomas and should be assessed accurately and robustly. However, the methods used for IDH1/2 testing are not fully standardized. The purpose of this paper is to review the clinical significance of IDH1/2 mutations and the methods used for IDH1/2 testing. The optimal method for IDH1/2 testing varies depending on a number of factors, including the purpose, sample types, sample number, or laboratory equipment. It is therefore important to acknowledge the advantages and disadvantages of each method.