Abstract. Eight new cases of hyperostosis corticalis generalisata are described. All showed the same typical localization of the increased bone formation. In three children (ranging in age between seven and ten years) this was already clearly visible, even though not so marked as in the adults. The clinical picture was suggested on a photo of the skull taken at the age of two. The disease may therefore start at a very early age, and then may be correlated with the often occurring facial paralysis, which in the beginning was not rarely transient. Early operation is certainly indicated in these patients. All eight patients proved to be related to each other. The pedigree chart is indicative of the autosomal recessive nature of the disease. In six adult patients suffering from this disease the iso-enzyme pattern of alkaline phosphatase was examined. The bone fraction was present in all cases, although in two cases alkaline phosphatase was not increased.