The widespread use of the routine EEG in clinical practice was a major development in the treatment of patients with ill-defined spells thought to be epileptic. Not every finding on the EEG is suggestive of epilepsy, and the EEG is subject to overinterpretation, which may lead to misdiagnosis and incorrect treatment. Although supplemented by other procedures, the EEG remains a cost-effective and noninvasive way to diagnose spells. To enhance further the diagnostic use of the EEG, it is important to determine how strongly patterns are correlated with clinical seizures. The authors studied one EEG pattern, lateralized bursts of [theta], and found the rhythmicity of the pattern to be most strongly correlated with seizures.