Over the years of cancer investigation a lot of discoveries in this field were made, and many associations between various biological carcinogens and cancer were revealed. Some of them are credibly determined, thus these infectious agents (human papilloma virus, hepatitis B virus, hepatitis C virus, Epstein-Barr virus, human herpes virus 8, human T-cell lymphotropic virus 1, human immunodeficiency virus, Merkel cell polyomavirus, Helicobacter pylori, Opisthorchis viverrini, Clonorchis sinensis, Schistosoma haematobium) are recognized as carcinogens and probable carcinogens by International Agency for Research on Cancer (IARC). The problem is of large importance, since share of infectious agents-related cancer cases is steadily increasing, reaching 25% according to certain estimates. It is worth noting that many of cancer cases are caused by infectious agents other than «conventional ones» like HPV, EBV, HBV, HCV, H.pylori etc. In recent years, a number of significant breakthroughs in the field were performed, such as the discovery of the microbiota role in cancer causation.

Preface.- The Criteria of Inclusion of Infectious Agents in the List of Biological Carcinogens.- General Mechanisms of Biological Carcinogenesis.- The Role of Bacteria in Cancer Development.- The Role of Protozoa in Cancer Development.- The Role of Helminths and Fungi in Cancer Development.- Organ Microbiota in Cancer Development: the Holy Grail of Biological Carcinogenesis.- Conclusions: Are We There Yet?