The invasion of Bruch's membrane and subsequently the subpigment epithelial and subretinal spaces by proliferating choroidal capillaries are prominent features of age-related macular degeneration. To facilitate study of this process, pure cell lines of bovine choroidal microvessel endothelium and pericytes were isolated and propagated in cell culture media. Their biological and biochemical properties are described. Choroidal microvascular endothelial cells displayed the characteristic cobblestone morphology, required fibronectin or gelatin for attachment to plastic culture dishes, displayed contact inhibition of growth and spontaneously formed tubules in culture. These cells contained antigens for Factor VIII and were able to phagocytize acetylated-low density lipoprotein. Choroidal microvascular pericytes were nonrectangular in shape and did not require substrate attachment factors. They were unable to form tubules in culture, were Factor VIII antigen negative, were unable to phagocytize acetylated-low density lipoprotein and did not display contact inhibition of growth. Choroidal microvascular pericytes contained antigens for muscle and nonmuscle actin.