The case of a three-year-old boy with the Smith-Lemli-Opitz syndrome is reported. In addition to the constellation of skeletal and genital anomalies classically described in this syndrome, this patient had spontaneous opsoclonus-like eye movements, strabismus, lack of visual following responses and of opticokinetic reflexes. At autopsy the cerebellar vermis was found to be absent. There were retinal hemangiomas. Microscopical examinations showed loss of Purkinje cells and extensive neuronal degeneration within dentate nuclei, associated with patchy demyelination of cerebellar peduncles and central white matter. These findings may contribute to the explanation of the pathophysiology of opsoclonus and some of the neuro-ophthalmological findings.