Clinical and laboratory findings of 25 patients with classical Cockayne syndrome (CS) are reviewed. A history of consanguinity was present in 21 patients, and 15 patients had at least 1 affected sibling. Apart from the cardinal features of dwarfism, microcephaly, and mental retardation, the most consistent clinical features included photosensitivity (84%), gait disturbances (84%), progeroid appearance (84%), and ocular abnormalities (88%). The most consistent laboratory findings comprised abnormal nerve conduction (slowed conduction in 13 of the 16 cases with an ENMG), and an abnormal brainstem auditory evoked response (BAER) and/or audiometry (abnormal in 13 of the 17 cases in whom either one of them were available). Cerebral atrophy and calcification of the basal ganglia were the next more common laboratory findings. Clinical criteria are useful in most instances in the diagnosis of CS. In patients in whom the clinical features are controversial for a diagnosis of Cockayne syndrome, studies directed to disorders of myelination involving both peripheral and central nervous systems in conjunction with audiometry may aid in the diagnosis.