Tomato lectin is a very stable glycoprotein containing about 50 percent arabinose and galactose. This lectin is composed of a single polypeptide of about 100,000 daltons that may form aggregates in solution. Like other lectins that bind N-acetylglucosamine oligomers, tomato lectin prefers trimers and tetramers of this sugar. Tomato lectin, although sharing some specificities with potato, Datura lectin and wheat germ agglutinin, has been reported to be dissimilar in many respects. Tomato lectin binds well to such glycoproteins as glycophorin and Tamm-Horsfall glycoprotein.