We participated in a cooperative study on ClO 2 inactivation of enteric viruses in water mentioned earlier (Olivieri et al. 1983 ). The primary target was PO1; but we included a porcine enterovirus, an RNA bacteriophage (f2), and a DNA bacteriophage (/X174). Because these had mutually exclusive host ranges, all the four were included in the reaction mixture and assayed individually in the samples. Most similar to the PO1 in inactivation was the /X174; least similar to the PO1 was the porcine enterovirus, which proved much more sensitive than any of the other three to ClO 2 : see Surrogates, next section. RNA infectivity of the PO1 was apparently little affected by ClO 2 . HAV in tap water and in strawberry wash water was inactivated by ClO 2 at 4 ppm; ClO 2 was less efficient at inactivating HAV in experimentally contaminated strawberries, which were better disinfected by heat treatment (71.7°C, 60 min) after the strawberries had been made into puree (Mariam and Cliver 2000a) .