Aerosolized viruses were passed through a high-intensity ultraviolet (UV) cell. This cell consisted of a long cylindrical aluminum tube [diameter, 7 in. (17.7 cm); length, 36 in. (91.4 cm)] with a highly reflective inner surface and a longitudinally extending helical baffle system which directed airborne particles in close proximity to a centrally located UV lamp. After having been passed through the UV cell, viral aerosols were collected with an Andersen sampler, and viral concentrations were determined by plaque assay methods on tissue cultures. Inactivation rates of greater than 99.9% were obtained for Coxsackie, influenza, Sindbis, and vaccinia viruses, and slightly less for adenovirus (96.8%), when the aerosols passed through the UV cell at 100 ft(3)/min. At aerosol flow rates of 200 ft(3)/min, inactivation rates were slightly lower; 91.3 for adenovirus, 97.5 and 96.7 for Coxsackie and Sindbis, respectively, and greater than 99.9% for influenza and vaccinia viruses.