A brother and sister suffering from hyperostosis corticalis generalisata familiaris (van Buchem's disease) are described. Both presented in early adult life with signs and symptoms of raised intracranial pressure and underwent partial craniectomy. Following surgery normal intellectual function was maintained and both survived to old age. In later life one showed cerebellar deficit due to bony encroachment of the posterior cranial fossa, while the other had a spastic paraparesis due to spinal cord compression. Several other siblings were affected by this disease which appears to be transmitted as an autosomal recessive gene.