N-chlorotaurine, an essential weak oxidant produced by stimulated human leukocytes, is known to have bactericidal, fungicidal and vermicidal properties. This study for the first time demonstrates its virucidal activity. By viral suspension tests at incubation times between 5 and 60 min, virus titers of both Herpes simplex virus type 1 and 2 were reduced about 1.3-2.9 log10 and 2.8-4.2 log10 by 0.1 and 1%, (5.5 and 55 mM) N-chlorotaurine, respectively. Virus titer reduction of adenovirus type 5 between 15 and 60 min was 0.5-2.0 and 0.6-4.0 log10, respectively, by the same concentrations of N-chlorotaurine. These findings support a contribution of N-chlorotaurine in destruction of pathogens during inflammatory reactions and also the possibility of its application as an antiviral agent in human medicine.