Lymphatic endothelial cells isolated from bovine mesenteric lymphatic vessels were cultured and characterized. Lymphatic endothelial cells grew as a monolayer displaying an elongated morphology in preconfluent primary cultures. When confluent, the cells exhibited a polygonal morphology to form a "cobblestone" pattern previously described for cultured vascular endothelium. All culture lymphatic endothelial cells expressed Factor VIII-related antigen and bound Ulex europaeus I lectin. Ultrastructurally, cultured lymphatic endothelium was characterized by the presence of Weibel-Palade bodies as well as the usual cytoplasmic organelles.