The lectin from Phaseolus acutifolius var. latifolius has been purified to homogeneity by affinity chromatography using stroma-sephadex, gel filtration and electrofocusing. The purified lectin consists of four subunits of 21 Kd molecular mass each one with 7.4% w/w total carbohydrate. Red cells of human and animal species, are agglutinated but are not inhibited by a series of sugars. Mitogenicity and immunosuppressive activities were demonstrated. Agglutination requires magnesium and calcium ions.