Objective: The objective of our study was to investigate the effects of chronic haloperidol administration on glutamate dehydrogenase activity and GABA level. Methods: We used ex vivo magnetic resonance spectroscopy along with high performance liquid chromatography to analyze forebrain tissue from rats administered oral haloperidol for 40 days. Results: Haloperidol administration for 40 days decreases the receptor binding of GABA and GABA levels at dose of 5mg/kg bw, 1.0 mg/kg bw, and 0.5 mg/kg bw and the activity of glutamate dihydrogen are increases significantly at the dose of 1.0 mg/kg bw, and 0.5 mg/kg bw Conclusion: Chronic haloperidol administration in rats appears to increase forebrain GABA and glutamate dehydrogenase activity. Studies exploring these processes in subjects with schizophrenia should take into account the potential confounding effects of antipsychotic medication treatment.