in the spring of 1974 the first 10,500-shp towboat went into service on the lower Mississippi River. This event raised the level of horsepower in river towboats to a new high - approximately 50 percent greater than that which existed only four years earlier. The design of these new vessels made use of service-tested features wherever possible, but the dramatic increase in horsepower dictated that many design parameters be extrapolated and not based on anything that had been done previously. This paper describes the design of one of the boats in this class which the authors believe is typical. It includes the basis for the design and many of the factors that were considered in arriving at the specific features included.