A long-term culture of choriocapillary endothelial cells (CCE) from bovine eyes has been established. We developed a micromanipulative technique with a dissecting microscope for isolation of choriocapillary sheets after a prolonged trypsinization of choroid tissues. We then used a cell sweeping technique to ensure a culture free of nonendothelial cell contamination. The cloned CCE possessed most morphological features and biochemical markers of capillary endothelial cells from other species and other origins. The CCE produced Factor VIII-related antigen and angiotensin-converting enzyme. The CCE phagocytized acetylated low density lipoprotein. The cell cycle time of CCE grown in a medium with sufficient soluble growth factors was dependent upon fibronectin (FN) coating concentrations. At a low concentration of FN (0.5 microgram cm-2) the cell doubling time was 42 hr, whereas at high FN (2 micrograms cm-2) the doubling time was 22 hr. The characterized choriocapillary endothelial cells produced by this method may be useful for studies of choriocapillary angiogenesis under physiological and pathological conditions.