Environmental surfaces may be contaminated with viruses and contribute to their transmission. Concerns have arisen in trying to control viruses because of an increasing incidence of viral infections. Ozone is considered to be a promising method to inactivate viruses on surfaces. In this investigation, the effects of ozone concentration, contact time, different capsid architecture of viruses, and relative humidity (RH) on inactivating viruses by ozone were evaluated. The authors observed that the survival fraction of viruses on surfaces decreased exponentially with increasing ozone dose. Viruses required ozone doses of 20-112 min(mg/m3) (contact time [min] multiplied by ozone concentration [mg/m3) for 90% inactivation and 47-223 min(mg/m3) for 99% inactivation. The ozone dose for 99% inactivation was two times higher than for 90% inactivation. The required ozone concentration at 85% RH was lower than at 55% RH. In summary, ozone should be an effective method for reducing the viral number between 1 and 3 logs on surfaces.