The progress of the Two-Phase Flow research is divided into four stages. These periods are 1948-1959, 1960-1970, 1971-1979, and 1980-1988. In this 5th Report, a history of the development of once-through boilers, and the related progress of researches on two-phase flow, the development of research on distribution of flow rate in evaporator tubes and dynamic behavior of steam generators in the secod stage has been described.