The suitability for field use of heating up to 80 degrees C and adding six different virucidal chemicals for decontamination of drinking and surface water was investigated using the viruses of Polio (vaccine strain), ECBO, Reo, bovine Parvo, HCC, Pseudorabies, ND and Vaccinia. The Parvovirus (concentration 10(5) TCID50/ml) heated to 80 degrees C could not be inactivated completely in drinking water within one hour; the Reovirus could after one hour only at 60 degrees C. The other viruses used lost their infectivity at 56 degrees C within 60 minutes or at 60 degrees C within 20 minutes respectively. Heating therefore seems to be too circumstantial a method for viral decontamination of water and unreliable under field conditions. As to the chemical water additives tested, chloramine-T, hydrogen peroxide and sodium peroxide proved to be unsuitable in spite of virucidal activity. The amount of their concentration necessary for reliable virus inactivation makes the water unfit for drinking. Iodine, a calcium hypochlorite sample and potassium permanganate were useful. Because of its constant reaction in drinking water together with additional advantages, iodination of water would seem to be the best method at present for viral water decontamination usable under field conditions.