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Half-gram quantities of phytohemagglutinin lectins are purified from saline extracts of red kidney beans (Phaseolus vulgaris) by affinity absorption on porcine thyroglobulin-Sepharose. All of the mitogenic and erythroagglutinin activity of the saline extract is removed by this absorbent, and 74% of the original erythroagglutinating activity elutes from the affinity absorbent representing a 25-fold purification. Five distinct proteins appear in the polyacrylamide gel electrophoresis of the affinity absorbent eluate. Although all five proteins specifically bind to porcine thyroglobulin, the cathodal migrating proteins bind more strongly than the anodal migrating proteins. The most cathodal proteins are potent erythroagglutinins. This simple, efficient method is used to prepare all the active components of the phytohemagglutinin family in large yield and high purity.