Routine and quantitative EEG analysis in Gilles de la Tourette's syndrome. Gilles de la Tourette's syndrome (GdlT) is a neurobehavioral disorder, with a reportedly high frequency of EEG abnormalities. We performed EEGs on 48 consecutive patients with GdlT, and frequency analysis in 26 patients (17 males), and compared the results with those from age- and sex-matched normal controls. Routine 18-channel EEG revealed minimal diffuse nonspecific slowing in only 3 of 48 patients (6%) and in 2 of 26 controls (7.7%). The frequency analysis of the EEG of the 26 GdlT patients and their normal controls showed similar brain activity. We conclude that no significant differences exist between the EEG activity in GdlT patients as compared with that in sex- and age-matched controls in routine as well as in quantitative EEG. 