Concanavalin A (Con A) lectin is isolated from Jack beans (Canavalia ensiformis) and purified by affinity chromatography. The molecular weight of the lectin is 104 kDa. It has broad applicability and is the most widely used lectin within molecular biology research. Con A binds specifically to α-Mannose, α-Galactose structures found in sugars, glycoproteins and glycolipids . The lectin has been utilized in hormone receptor studies, mitogenic assays and for characterizing normal and malignant cells (cancer cells are readily aggregated by Con A while normal cells are not). Con A can also initiate cell division (mitogenesis) principally acting on T-lymphocytes . Immobilized Con A has been used in affinity chromatography purifications of a wide variety of glycoproteins and cellular structures. Polyacrylamide gel electrophoresis in SDS of Con A from Jack beans yields three major bands corresponding to molecular weights 27, 13 and 10 kDa. One minor band is visible at 18 kDa. Medicago’s Con A is supplied as a white lyophilized powder from a buffer containing 0.5 mM MnCl2, 0.5 mM CaCl2, no preservatives are added. The identity is determined by SDS-PAGE (Figure 1) and the protein content by spectrophotometry (Figure 2). The lectin is available in vials containing 250 mg or 100 mg lyophilized powder and the product is to be used for laboratory work only.