Electroencephalographic investigation of 21 patients with delusional misidentification syndromes (11 with the syndrome of Capgras, 7 with the syndrome of Frégoli, 2 with the syndrome of intermetamorphosis and 1 with the syndrome of subjective doubles) revealed a high abundance and severity of abnormalities. The findings are discussed within the framework of a possible organic (and more specifically dysrhythmic) contribution to the pathogenesis of these syndromes.