The separation of calli and recovery of extracellular polysaccharides (TPS) by filtration from culture broth of Polianthes tuberosa were studied. The solids (calli or cell debris) to be separated included particles smaller than TPS molecules. Dead-end filtration of calli alone at a constant flow rate produced a compressible cake layer, but the use of filter aids such as diatomite, silica or cellulose powder resulted in an incompressible cake layer under the operational conditions, and the separation of calli and recovery of TPS were achieved. This result is attributable to electrical repulsion among calli, filter aids and TPS molecules. Addition of 3% NaCl and small filter aids (average particle size 27.9 mu m) allowed stable calli separation, giving a filtrate of 95% optical transmittance and TPS recovery of almost 100%.