We sought to determine whether neuronal dysfunction throughout the temporal lobes of children with temporal lobe epilepsy (TLE) is already as severe at the time of diagnosis as it is in patients with long-standing intractable TLE (INT-TLE). Proton magnetic resonance spectroscopic imaging was used to measure N-acetylaspartate/creatine (NAA/Cr) ratios in the temporal lobes of five consecutive children with newly diagnosed TLE (ND-TLE), five with INT-TLE, and 30 normal control subjects. The median age of those with ND-TLE and those with INT-TLE did not significantly differ (P = 0.92). All five patients with ND-TLE had bilateral reductions in the NAA/Cr ratio. Two of the five patients with INT-TLE had bilateral reductions in the NAA/Cr ratio; three had unilateral reductions in the NAA/Cr ratio. In the three patients with lesions the NAA/Cr ratio decrease extended outside these lesions. No significant differences were detected in any temporal lobe region between the ND-TLE and INT-TLE groups. The severity of the neuronal dysfunction in the children with ND-TLE was at least as severe as in those with INT-TLE and was not restricted to one temporal lobe, implying that the neuronal abnormalities observed in patients with TLE occur before the clinical manifestations.