A case is reported of polyagglutination with features of both Tk and Th activation associated with an acquired B antigen. Reactions with polybrene, Glycine soja, and Bandeiraea simplicifolia II indicated the presence of Tk activation. However, the reactivity of the patient's erythrocytes with Arachis hypogoea was greatly reduced by treatment with ficin, indicating the concomitant presence of Th activation.