Suspensions of herpes simplex virus types 1 and 2, cytomegalovirus, and parainfluenzavirus type 2 were inactivated within 24 h when treated at 37 degrees C with 1 mg (5.05 mM) of copper-catalyzed sodium ascorbate per ml. The infectivity titer of respiratory syncytial virus was reduced substantially after 24 h but required 48 h for inactivation. Under these conditions, inactivation of these viruses was also successfully achieved with 5.68 mM catalyzed ascorbic acid. Copper (Cu2+), when added with the ascorbate solution at 5 micrograms/ml (0.022 mM), exhibited a catalytic effect on the inactivation of these viruses. The rate of inactivation was affected by the incubation temperature, time of exposure, and the virus concentration. Ascorbate concentrations as high as 10 mg/ml (50.5 mM) demonstrated only a minimum increase in effect on viral inactivation. The loss of infectivity did not alter either the hemagglutination or complement fixation qualities of the antigens.