We report the clinical history of two brothers with the classical Cockayne syndrome. The main manifestations consisted of cachectic dwarfism, mental retardation, intracranial calcifications, microcephaly, enophthalmia, senile appearance, joint hypomotility and skin photosensitivity. In one of these children, who died at 10 years of age of bronchopneumonia, necropsy studies revealed a variety of anomalies, mainly encephalic, which included an arachnoidal cyst at the base of the cerebellum, a defect apparently previously undescribed in patients with this syndrome.