Localized in vivo proton magnetic resonance spectroscopy (MRS) was performed to evaluate metabolic alterations in the right and left frontal lobe before and after neuroleptic treatment of schizophrenic patients (n=24) and a group of healthy normal subjects (n=20). Proton metabolic ratios obtained from the 8㎤ yokels in the right and left frontal lobe were compared with the clinical assessment of PANSS for each subject. There was no significant difference in the metabolic ratios between the right and the left frontal lobes in either the schizophrenic group or the control group, indicating no laterality. Compared with those of the normal control group, NAA/Cr and (GABA+Glu)/Cr ratios of the schizophrenic patients showed significantly lower (p=0.023) and higher (p=0.005) value, respectively. The (GABA+Glu)/Cr ratio of the schizophrenic patients was generally decreased after neuroleptic treatment, while the NAA/Cr ratio was not changed. Significant correlation between the (GABA+Glu)/Cr ratio and the clinical symptom scores assessed by PANSS was established. The present study supports the “hypofrontality” hypothesis of schizophrenia on the basis of the altered metabolic ratios before and after neuroleptic treatment.