With growing interest in battery electric vehicles, the use of the disc armature motor, with its inherent high efficiency and power density, is investigated for such applications. With the need to establish an optimum design for a given specification a computer-aided design procedure is developed with due regard to the motor operating principles and the performance of existing prototypes. This procedure presents a large number of alternative designs to meet a specification in terms of the voltage , power and speed requirement. The magnet material to be used is the only other necessary input to the program, although various restrictions may be applied if desired. With the use of a duplex wave winding sometimes called for, and in certain cases alternative methods of connection available, a study is made of a particular winding in terms of the e.m.f.s generated in the primary armature paths and those short-circuited by the brushes. It is shown that an optimum arrangement exists and if this is not specified,significant deterioration in motor performance results as verified experimentally. The thermal performance of the motor is discussed and appropriate rating conditions are proposed as an aid to future design. Finally the use of the motor in a practical application is studied with the aid of a simulation model of an electric vehicle and practical road testing. It is shown that improvements in overall vehicle performance result when a disc armature motor is specified in place of a comparable series wound machine.