The Turbine Design System (TDS) is a time sharing computer system developed for preliminary design and performance evaluation of axial flow turbines having up to ten stages. TDS is an interactive, modularized system incorporating aerodynamic, heat transfer and structural analyses in a contiguous arrangement. Each task oriented module addresses one major facet of the design process. This paper discusses the overall system philosophy and organization, the input/output data flow, the tasks performed, and the functional utilization of the system. Selected results of a sample case are shown.