Though the surgical treatment for medial temporal lobe epilepsy yields a high success rate, more studies are needed in order to determine the most efficacious pre-operative algorithm. The authors studied the relationship between surgical outcome and the localization results of various pre-operative diagnostic tests to assess the predictive value. Seventy-one consecutive patients who had undergone anterior temporal lobectomy with amygdalohippocampectomy with the diagnosis of non-lesional medial temporal lobe epilepsy, who had been followed up more than 24 months, were analyzed retrospectively. Electroencephalogy (EEG), magnetic resonance imaging (MRI), proton emission tomography (PET), single photon emission computed tomography (SPECT), the Wada test, and neuropsychological testing were analyzed. There was no diagnostic test that was found to have a statistically significant relationship between Engel Class I outcome and localization results (P& 0.05). SPECT, neuropsychological testing, and the Wada test all had less predictive values (P< 0.01). EEG and PET had comparable predictive values for Engel Class I with MRI (P& 0.05). No single diagnostic test alone is sufficient to make a diagnosis of non-lesional medial temporal lobe epilepsy. MRI, EEG and PET had comparable predictive values for Engel Class I. SPECT, neuropsychological testing, and the Wada test had less predictive values.