In this review, we discuss possible models of bacteriophage-virus interactions. The first is based on the mechanism by which phages may interact indirectly with viruses. Its essence is that bacteriophage-derived nucleic acid may inhibit pathogenic virus infection. It seems that this phenomenon can be partly explained on the basis of interferon induction. We also discuss a study by Borecky's group (conducted over two decades ago) which provided some clinical data on the effectiveness of the application of native bacteriophage RNA in the treatment of viral infections. The second interaction model is based on the direct competition of bacteriophages and viruses for cellular receptors for viral cell-entry. The use of bacteriophages as inducers or displayers of antibodies with antiviral action is considered as the third model. In this part of the article, we also discuss other data and hypotheses on conceivable interactions between bacterial and animal viruses. As our current supply of antiviral drugs is quite limited, using natural agents such as bacteriophages as a weapon against pathogenic viruses could be an attractive and cost-efficient alternative, and further studies are urgently needed to test this possibility.