The literature review is devoted to the modern concept of human betaherpesvirus 6 (human herpesvirus 6; HHV-6). The analysis of the literature mainly for the last five years was carried out. The article provides a brief background on the history of the discovery of viruses, highlights the taxonomy of HHV-6, new views on the etiological features of the HHV-6A and HHV-6B viruses, in particular, the possibility of their gene integration. Differences between HHV-6A and B are described. Modern views on the etiological relationship of various diseases of the central and peripheral nervous system, а heart, other organs and systems with HHV-6A and HHV-6B are presented. There have been cases of infectious mononucleosis associated with HHV-6, as well as exanthemа subitum that is mostly typical for children under 2 years old. Modern ideas about the possibilities and problems of HHV-6 infection laboratory diagnosis and treatment of children and adult are given. Obtained data points out necessary of a unified protocol creation for the examination and treatment of HHV-6.