Methods are described for the preparation of bacterial immunoabsorbents consisting of organisms dispersed in agar beads 50 to 200 μm in diameter. The concentration of organisms could be made extremely high and columns prepared had sufficient capacity to enable them to be used for a number of purposes, but particularly for the removal of cross-reacting agglutinins from production batches of type-specific antisera. The absorptive capacity of these columns was regenerated after absorption by the elution of agglutinins with low pH buffers. Results obtained from the use of these immunoabsorbents are presented. Images