MGMT (O6 methyl guanine methyl transferase) is a gene involved in DNA repair. Its mechanism of action is to remove alkyl groups created by alkylating chemotherapy and therefore induces chemoresistances. Recent studies show that this gene expression seems to be related to the promoter's methylation, which could predict a possible chemosensitivity. The study of MGMT could be of some therapeutic and prognostic interest. Few series of oligodendrogliomas have been published and their results appear to be controversial. This is probably due to both tumour heterogeneity and multiple parameters associated with chemosensitivity. To date, it thus appears difficult to choose the adjuvant treatment according to the sole status of MGMT.