Various types of energy-absorbing bumper system are in use today. Apart from the function of protecting the vehicle body at a minor impact, the bumper is now required to be as lightweight as possible since its weight is a major factor for a number of vehicle attributes.While cutting down on the vehicle weight is all important to improve driving performance, handling and stability, and fuel economy, weight reduction for the bumpers located the farthest from the vehicle's center of gravity is a critical factor which governs the vehicle's yaw moment, thus greatly influencing the car's handling and stability. (Generally, the vehicle's yaw moment is said to increase with the square of the distance from the bumper to the center of gravity.) In a lightweight sports car expected to give exact dynamic response to the driver's command, lightweight bumpers are crucial.To realize lightweight bumpers for the Mazda Miata MX-5, we developed a lightweight blow-molded bumper beam. This paper describes its features and priority items, along with the advantages gained.