Pleated membrane filtration capsules, utilizing cross-flow and liquid membrane technology, were evaluated for use in poliovirus extraction from inoculated oyster tissue homogenates. The filtration technique is fast and less complex than other extraction procedures. Capsules filtered an average of 450.3 ml of a one liter homogenate within 20 min. Filtrates were clear and contained a mean virus recovery of 46.1% in non-dialyzed samples that were concentrated by ultrafiltration. Cytotoxicity was not observed in cell culture monolayers inoculated with non-dialyzed, water-dialyzed or bufferdialyzed concentrates. Dialysis and concentration procedures did not significantly reduce the number of viruses in the filtrates.