AbstractOral dyskinesias may occur spontaneously or be induced by medications such as antipsychotics and antidepressants. In this study, single voxel proton magnetic resonance spectroscopy was used to compare metabolite levels in the striatum for (1) 12 patients with drug‐induced tardive dyskinesia (TD), (2) 12 patients with spontaneous oral dyskinesia (SOD), (3) 8 antidepressant‐treated patients without TD, and (4) 8 control subjects. Statistically significant reductions in the choline/creatine (Cho/Cr) ratio were measured for the drug‐treated patients with TD (−13%, P = 0.020) and SOD patients (−12%, P = 0.034) relative to control subjects. In comparison with antidepressant‐treated patients without TD, drug‐treated patients with TD showed a non statistically significant reduction in Cho/Cr (−11%, P = 0.079). All other metabolite ratios (N‐acetylaspartate (NAA)/Cr, myo‐inositol (mI)/Cr, glutamine + glutamate (Glx)/Cr, macromolecule + lipid (MM+Lip)/Cr, NAA/Cho) were unaffected by either type of dyskinesia. The observed Cho/Cr reduction in dyskinesia patients suggests decreased membrane phosphatidylcholine turnover, which provides free choline as precursor of molecules responsible for cellular signal transduction. © 2007 Movement Disorder Society