The growth of endothelial cells from small segments of human great saphenous vein was investigated for possible functional studies of endothelial cell properties and endothelialization of cardiovascular prosthetic graft materials. Growth in medium containing fetal calf serum or human serum was compared, and the effects of adding compounds that increase intracellular cyclic adenosine monophosphate levels, that is, cholera toxin and isobutylmethylxanthine, were also examined. It was shown that human serum was more efficient in stimulating cell growth than fetal calf serum at all concentrations tested. It was also shown that the addition of cholera toxin and isobutylmethylxanthine significantly potentiated growth. Minimal Essential Medium with the addition of 40% human serum and cholera toxin (1 nmol/L) and isobutylmethylxanthine (33 mumol/L) was shown to be optimal. From a single segment (3 to 5 cm), 20 x 10(6) human saphenous vein endothelial cells corresponding to 2000 cm2 or more could be achieved after 3 to 4 weeks in culture. The human saphenous vein endothelial cell cultures retained their cobblestone appearance, expression of von Willebrand Factor (vWF)-antigen, and capacity for prostacyclin production after six passages. We suggest that this provides a practically useful method for studies of cultured endothelium and possibly for pre-endothelialization of cardiovascular prosthetic materials.