The inactivating effect of anodic oxidation on viruses performed in an experimental electrolytic polarization unit was investigated with 11 different viruses suspended in tap and superficial water. Furthermore attempts were made to define the influence of factors important in experimental and water respect. Using concentrations up to 10(4) infectious units per ml representing a multiple quantity of the virus demonstrable in contaminated environmental waters all the viruses investigated could be inactivated reliably and rationally when suspended in tap water, more easily however in water of improved conductivity, by passing the current leading unit once. Anodic oxidation represents a fast and rational not denaturating method for decontamination of virus containing waters. Varying conditions of a water as well as bacterial contamination, so far remaining within naturally occurring scope, have only little or no influence on the inactivating effect on viruses. The applicability of the method is discussed briefly.