Sponges are an ecologically important component of marine and freshwater bodies sponge community includes a variety of microorganisms (fungi, algae, archaea, bacteria) and viruses. Viruses regulate the abundance, composition and biodiversity of numerous aquatic microorganisms and other hydrobionts, and, in general, influence significantly on the functioning and ecological state of water bodies. The abundance and diversity of viruses in sponge community are likely very significant, considering a great number of their potential hosts. However, the diversity and importance of viruses have been little studied compared to other sponge-associated microorganisms, and the role of viruses in the sponges (especially in freshwater ones) remains largely unknown. The aim of our work is the study of the genetic diversity of viruses in the associated community of the endemic Baikal sponges using metagenomic approach.