Double stranded RNA obtained from non-permissive E. coli cells infected with f2-phage was tested in 5 hospitals in viral dermtoses such as herpes simplex recidivans, herpes zoster, male genikeratonconjunctivitis herpetica and conjunctivitis lignosa. The results of clinical tests indicate that the preparation of phage double stranded RNA applied topically is harmless for man and has, in the majority of cases, a beneficial effect in the disease. This conclusion was based on the judgment of physicians, opinion of patients expressed in a questionnaire, and, results of a double-blind experiment.