Prorenin (PR) was localized by electron microscopic (EM) immunostaming of cryo-ultramicrotomy sections of human ciliary body and correlated with light microscopic immunoskuning. Both layers of the ciliary epithelium contained the prohormone. However, density was much higher in the adjacent extracellular spaces, particularly in the vitreous cortex. This observation adds further evidence to a role of the the ciliary epithelium in the transfer, storage or synthesis of components of a putative ocular renin angiotensin system.