Ulex europaeus agglutinin I binds to many glycoproteins and glycolipids containing α-linked fucose residues, such as ABO blood group glycoconjugates. This lectin preferentially binds blood group O cells and has been used to determine secretor status. It has been established as an excellent marker for human endothelial cells. DyLight 594 labeled Ulex europaeus agglutinin I has an appropriate number of fluorochromes bound to provide the optimum staining characteristics for this lectin. This conjugate is supplied essentially free of unconjugated fluorochromes.