Phosphorus magnetic resonance spectroscopic imaging has previously demonstrated localized metabolic abnormalities within the epileptogenic region in patients with temporal lobe epilepsy, including alkalosis, increased inorganic phosphate level, and decreased phosphomonoester levels. We studied 8 patients with frontal lobe epilepsy, finding interictal alkalosis in the epileptogenic region compared to the contralateral frontal lobe in all patients (7.10 +/- 0.05 vs 7.00 +/- 0.06, p < 0.001). Seven patients exhibited decreased phosphomonoester levels in the epileptogenic frontal lobe compared to the contralateral frontal lobe (16.0 +/- 6.0 vs 23.0 +/- 4.0, p < 0.01). In contrast to findings in temporal lobe epilepsy, inorganic phosphate level was not increased in the epileptogenic region. Based on values derived from normal control subjects, 5 patients had elevated pH in the seizure focus and 2 patients had decreased phosphomonoesters while none had abnormalities in the contralateral frontal lobe. These data suggest that magnetic resonance spectroscopy will be useful in the presurgical evaluation of patients with frontal lobe epilepsy.