Understanding the molecular biology of RNA viruses, e.g., the functions of viral RNA elements and proteins and their interplay with host factors, is essential in dissecting the mechanism of the pathogenesis of RNA viruses, as well as screening antivirals. This reprint presents the latest progress in the molecular biology of several RNA viruses and state-of-the-art technology used to study the molecular biology of RNA viruses and their interactions with host cellular proteins. Moreover, novel antiviral drugs and cell culture systems are described.