Fluorescein angiography has been used to demonstrate the in vivo hemodynamics and transudation from a retinal hemangioblastoma. This confirms the long held clinical impression regarding the pathogenesis of the retinal changes in this syndrome. The analogy between the pathogenesis of the retinal changes and those in the cerebellum is drawn. The value of fluorescein angiography as a criterion of successful treatment and method of early diagnosis is demonstrated.