Seven cases of infantile osteopetrosis are presented. Five of these were available for detailed clinical examination and 2 for retrospective review, including autopsy slides. Neurological deficits in these patients are reviewed. Involvement of the central nervous system parenchyma was suggested by observations of delayed development, ocular abnormalities, and reflex changes as well as radiographic and autopsy findings. Cerebral atrophy was present in several of our patients as well as some reported in the literature and may account for the ventricular enlargement found in many of these patients. Though hydrocephalus may be present, it is unclear that this is frequent or that it can occur without antecedent intracranial hemorrhage. The large head size is not accounted for by calvarial thickening or by hydrocephalus. Despite our patients' small stature, pituitary function appeared to be normal. Surgical decompression may stabilize cranial nerve function, particularly when the optic nerves are involved.