Endothelial cells grown in vitro are widely used for the study of vascular physiology and pathology. The high levels of serum supplementation normally used in endothelial cell culture may create problems in experimental design or in interpretation of results. A serum-free medium (SFM) has been designed specifically for culture of nonhuman vascular endothelial cells. Growth as well as retention of various physiological markers in this medium was demonstrated in large-vessel endothelial cells from bovine, porcine, ovine, and canine species. Cells from all species tested took up DiI-acetylated LDL. Factor VIII-related antigen was demonstrated in cultures of bovine and canine cells. Bovine and porcine cells were shown to have retained the ability to produce prostacyclin. Further supplementation of the SFM with various lipid-containing additives failed to stimulate either growth or prostacyclin production. PDGF produced by bovine, porcine, and canine endothelial cells was measured and found to be present at lower concentration than in serum supplemented cultures. All cells grown in SFM exhibited the histiotypic "cobblestone" morphology normally associated with cultured endothelial cells. While not optimized for culture of human endothelial cells, short-term growth < or = 4 passages) of human umbilical vein endothelial cells was achieved by supplementing the SFM with hydrocortisone, bovine pituitary extract, and epidermal growth factor.