Fifty individuals in nine families had von Hippel-Lindau disease. Nearly all of the morbidity and mortality of the entity is associated with six of its manifestations, each of which can be successfully treated. Retinal angiomatosis, which occurs in more than half of those affected, can produce blindness if not treated. Cerebellar hemangioblastoma, which is observed in one third of patients, is the most common source of initial symptoms and caused more than half of the deaths in the series. Medullary and spinal hemangioblastomas occur infrequently. Pheochromocytoma is common in certain families and is usually bilateral. Renal cell carcinoma, which generally arises at a later age, may befall the patient who is successfully treated for the tumors that occurred earlier. However, this tumor can be treated also, if there is early detection.