Aim:Role of extrachromosomal DNA in cancer and the consequences of mutations are unclear. However, mitochondrial DNA (mtDNA) variants in the D-loop region have been suggested to be associated with different clinical parameters and proposed as controversial prognostic markers. Impaired function of mitochondria cannot be tolerated by highly energy requiring brain cells. Therefore, we have focused on the regulatory region D-loop which is thought to cause no growth disadvantage for cells. Our aim is to investigate the effect of mtDNA variants mainly in D-loop on glioma biology.Material and Methods:Sanger sequencing of D-loop (15971 - 16451 bp) for 52 glioma patients was performed and the variations were statistically analyzed for gender, WHO classification, morphological grade, IDH / TERT status.Results:Total of 122 variations (51 unique) was identified in 52 patients. C16223T, T16189C, T16311C and T16126C variants were frequently detected. Total variation number was statistically non-significant among the analyzed categories. When individual variants were considered, T16311C and T16224C were statistically significant for WHO classification (p=0.033), morphological grade (p=0.036) and gender (p=0.039), respectively.Conclusion:Total variation number in D-loop was not found to be related with clinical variables. Our data suggests that individual variants may play critical role in glioma biology.