Background: Oligodendroglial neoplasms with combined loss of chromosomes 1p a nd 19q may have a good prognosis and respond to procarbazine- lomustine (CCNU) - vincristine (PCV)- chemotherapy. Objective: To determine whether single voxe l magnetic resonance spectroscopy (SV- MRS) obtained through routine clinical p ractice distinguishes between histopathologic and genetic subtypes of oligodendr oglial tumors. Methods: Forty- eight patients with oligodendroglial tumors (19 oligodendrogliomas and 29 oligoastrocytomas) underwent molecular genetic analysis to determine allelic imbalance in chromoso mes 1p36 and 19q13. SV- MRS was obtained pretherapy to determine tumor metaboli te ratios. Results: Grade III oligodendroglial tumors had higher choline (Mann- Whitney; p=0.002), methyl lipid (Mann- Whitney; p=0.002), and combined methyle ne lipid and lactate ratios (Mann- Whitney; p < 0.001)- than grade II tumors. Lactate did not distinguish between tumor types (Fisher exact test; p=0.342) or grade (Fisher exact test; p=0.452). There were no significant associations when tumors were analyzed according to histopathology or genetic subtypes. Conclusion : As a noninvasive diagnostic tool used in routine clinical practice, SV- MRS h as the potential benefit of determining oligodendroglial tumor grade but not sub types classified by histopathology or molecular genetics. MRS may be useful for determining the timing of therapy but is unlikely to predict chemosensitivity. Background: Oligodendroglial neoplasms with combined loss of chromosomes 1p a nd 19q may have a good prognosis and respond to procarbazine-lomustine (CCNU) - vincristine (PCV) - chemotherapy. Objective: To determine whether single voxel magnetic resonance spectroscopy (SV- MRS ) obtained through routine clinical p ractice distinguishes between histopathologic and genetic subtypes of oligodendr oglial tumors. Methods: Forty-eight patients with oligodendroglial tumors (19 oligodendrogliomas and 29 oligoastrocytomas) underwent molecular genetic analysis to determine allelic imbalance in chromoso mes 1 p36 and 19q13. SV Results: Grade III oligodendroglial tumors had higher choline (Mann-Whitney; p = 0.002), methyl lipid (Mann-Whitney; p = 0.002), and combined methyle ne lipid and lactate ratios (Mann-Whitney; p <0.001) - than grade II tumors. Lactate did not distinguish between tumor types (Fisher exact test; p = 0.342) or gr There was no significant associations when the tumors were analyzed according to histopathology or genetic subtypes. Conclusion: As a noninvasive diagnostic tool used in routine clinical practice, SV-MRS h as the potential benefit of determining oligodendroglial tumor grade but not sub type classified by histopathology or molecular genetics. MRS may be useful for determining the timing of therapy but is unlikely to predict chemosensitivity.