Tomato lectin, although sharing some specificities with potato lectin, Datura lectin, and wheat germ agglutinin, has been reported to be dissimilar in many respects. LEL binds well to glycophorin and Tamm-Horsfall glycoprotein and has been used effectively to label vascular endothelium in rodents. Biotinylated tomato lectin has an appropriate number of biotins bound to provide the optimum staining characteristics for this lectin. This conjugate is supplied essentially free of unconjugated biotins and is preserved with sodium sodium azide.