A further study of conditions for induction, determinations of activity and products of mRNAs translation of AVP having nonspecific antiviral activity from L-929 cells treated with poly(I) . poly(C) was carried out. Under conditions of superinduction of interferon the yield of AVP mRNA is reduced unlike that of interferon mRNA. Manifestations of the antiviral effect of AVP mRNA translation products do not seem to require the stages of transcription as dihydrorifampicin exerts no influence on this process. The inhibiting effect of actinomycin D is more likely to be associated with its effect on the energy of cells and synthesis of macroergic compounds of ATP type. Active AVP mRNAs from L-929 cells like interferon mRNA consist mainly of poly-A-deficient mRNAs. The sedimentation rate of AVP mRNAs differs from that of interferon mRNA and is about 10S. AVP mRNA translation products in ovocytes of Xenopus laevis, in contrast to control mRNAs, contain isoadenylate synthetase responsible for synthesis of 2'5'-oligoisoadenylate, a nonspecific translation inhibitor the mechanism of action of which consists in activation of cellular endogenous nuclease. The results suggest that the mode of development of the antiviral condition by activation of isoadenylate synthetase is similar in the cells treated with interferon and poly(I) . poly(C).