Abstract
SUMMARY Plaques were produced in mouse-embryo monolayers by infection with polyoma virus DNA in the presence of diethylaminoethyl-dextran. Optimum conditions for plaque assay were established and dose-response relationships for component I and component (II+III) polyoma DNA determined. Efficiencies up to 6 x lO 5 p.f.u.//zg, were obtained for component I DNA.