Cross-linked poly(N-benzyl-4-vinylpyridinium bromide) (BVP resin) was found to be very efficient in removing pathogenic human viruses from aqueous solution. In batch removal experiments using 50 g/1 of BVP resin at 35 °C. the level of infectivity in suspensions of enterovirus. herpes simplex virus, poliovirus, and human immunodeficiency virus was reduced 1000–100000 fold during a 2 h period. Those of coxsackievirus and echovirus were reduced 60–600 fold during 1 h contact. The haemagglutination titres of solutions of human rotavirus, influenza virus, human adenovirus. and Japanese encephalitis virus were reduced 16–256 fold during 30 min of contact. In removal experiments by a continuous flow column method for poliovirus. enterovirus. and coxsackievirus with initial infectivities of less than 105/ml, the infectivity of these viruses was no longer detectable in the effluent solution. For poliovirus, coxsackievirus, and echovirus with initial infectivities higher than 106, 99·8–99·9998% of the input viruses was removed as indicated by the reduction of infectivity.