OBJECTIVE To evaluate the clinical utility of mesial frontal semiology. DESIGN Retrospective case series. SETTING Tertiary epilepsy referral center. PATIENTS Part 1 of the study involved 152 patients who underwent frontal lobe surgery. Part 2 involved 253 patients who underwent non–frontal lobe surgery. MAIN OUTCOME MEASURES Inclusion criteria for both parts of the study were seizure localization by analysis of resection margins (mesial frontal, lateral frontal, orbitofrontal, nonfrontal) or intracranial exploration and an Engel class I outcome. In part 1, 84 patients had their habitual seizures analyzed by video encephalography using a semiology checklist of 47 items during the early phase (electrographic onset to 10 seconds) and late phase (rest of episode). Localization semiology was analyzed by χ2 test with Bonferroni correction and cluster analysis when occurrence exceeded 10% in at least 1 region. In part 2, 144 patients had their habitual seizures screened with mesial frontal semiology from the first part of study during the early phase only. RESULTS In part 1 of the study, the statistically significant localizing semiology for the mesial frontal region in the early phase was ictal body turning along the horizontal axis (57% of patients), crawling (57% of patients), restlessness (64.3% of patients), facial expressions of anxiety (42.9% of patients) and fear (35.7% of patients), grimacing produced by bilateral facial contraction (42.9% of patients), barking (32.1% of patients), head shaking (25% of patients), and pelvic raising (25% of patients) (all P < .001). In the late phase, recurrent utterance (21.4% of patients) was the additional statistically significant item (P < .002). In part 2 of the study, ictal body turning along the horizontal axis gave a 55.2% positive predictive value, which improved to 85.7% when clustered with restlessness, facial expressions of anxiety and fear, and barking. CONCLUSIONS Ictal body turning along the horizontal body axis and semiology with physiological movement are not only prevalent semiology items of mesial frontal lobe epilepsy but they distinguish mesial frontal from lateral frontal and orbitofrontal seizures.Arch Neurol. 2008;65(1):71-77-->