Whole microbial cells from an activated sludge seed were immobilised in spherical polyacrylamide beads using a shrink/swell procedure which increased cell viability more than 100-fold over the seed material. The process was optimised with respect to the seed concentration and incubation time. It was shown that the swell procedure was essential to achieve good immobilisation and that biofilm attachment to the beads made a negligible contribution to the immobilised biomass. The physical and biological properties of the immobilised beads were determined and found to settle well and resist mechanical abrasion. In addition, their preparation did not prove toxic to the immobilised biomass. The beads produced have many applications for instance in enhancing the biomass in wastewater treatment processes. In addition the immobilisation process could be applied to a wide range of microbial consortia including pure cultures of microorganisms.