The investigations of study the contact of algal viruses (strains of TvV and PtV) and their hosts (Tetraselmis viridis and Phaeodactylum tricornutum) by microcalorimetry method were carry more 15 years ago. Heat production of contact of algal viruses and their hosts (algae) measured by Biological Activity Monitor (BAM) is presented in graphics-thermogrammes in µW. It was shown that heat production of algae cultures growth (in control) will depend on such factors as the species of algae, their concentration and the growth stage (phase) of culture, nutrient content and lighting, and also of other factors of biotical and abiotical origin. Viral infection, in our opinion, is one of the most significant factors affecting the viability of algae and therefore on the amount of heat production of algae cultures infected with the virus. Interaction between algal viruses and sensitive algae culture leads to the production of virus and destruction (lysis) of host cells that manifests itself in reducing heat production in the experiment as compared with the control. The contact between the algal viruses with their hosts was accompanied by a decrease of heat production in the first hours of their interaction, but the best difference was observed after 10–24 h. We hope that this study can be used to study the contact of other viruses with host cells in order to assess the influence of various factors (UV, EMF, various substances and drugs) on this contact.