The substantial part of drag on an automobile is due to pressure. Therefore, a car must be designed which produces minimum pressure drag. The paper describes the effects of geometrical configuration of the rear part of a car on aerodynamic drag. Experiments were made on 1/5 scale models of fastback and notchback design. For a fastback car, the drag depends heavily on the angle of the rear window. At a certain critical angle, the drag shows a sharp peak. This peak drag can be reduced drastically by the tapering of plan form of the rear geometry. For the notchback design, one combination of the angle of the rear window and height of the trunk deck shows similar maximum drag. Methods of avoiding this large drag were found. The experiment was extended to the measurement of the wake structure by hot wire anemometers and total pressure tubes. The correlation between the wake structure and drag was clarified by the consideration of vorticity and circulation (a).