By affinity chromatography on Sepharose columns containing insolubilized ricinus agglutinin, all immunoglobulins of the Iga2 subclass and the polymers of IgA1 were retained and could be eluted with lactose. Monomeric IgA1 showed a more heterogeneous reaction with ricinus agglutinin. The major part was unretarded, whereas some of it was weakly bound to the column and could be eluted with lactose.