A simple method for drying virus on inanimate objects (cover slips) under vacuum in the cold is described. Following this procedure virus maintains high titers (10(6-7)) for periods of 1-3 wk at -70 degrees C depending on the virus. For virucidal assay of disinfectants, cover slips are exposed to medium simulating the disinfectant (virus control) or disinfectant in an upright position in an Ultra-Vu cuvette. Cover slips are readily removed and placed in tissue culture medium for dilution of virus and determination of virus titer. Cytotoxicity of disinfectant is determined by exposing cover slip without virus to disinfectant, then placing it in medium, diluting the medium and incubating with the indicator cells. The use of this technique results in high titers of virus on cover slips, which are inanimate objects requiring minimal manipulation. The titration of virus or cytotoxicity in microplates is cell, medium, serum, and labware economical.