The electroencephalograms of 50 parkinsonian patients with no convulsive antecedents were studied. EEG abnormalities were found in 20 patients (40% of the cases). The incidence of abnormal records was larger in the bilateral parkinsonian syndrome than in the unilateral one (52% and 25%, respectively). Paroxysmal abnormalities characterized mainly by bursts of theta waves were the most frequent ones (65% of the cases). Sharp activity found in the EEG patterns of three patients is emphasized. Alterations of the base rhythm were recorded in 30% of the abnormal EEG cases. The patient's age doesn't seem to have an important role in the genesis of the electroencephalographic abnormalities.