Federal mileage requirements for automobiles in 1985 have stimulated the use of lightweight materials for body components. Among the lightweight materials under consideration, reinforced RIM (RRIM) polyurethane is a leading contender and is therefore under current evaluation for several automotive body components including fenders, door panels, and rear quarter panels. In response to these new RIM application areas, the polyurethane raw material suppliers have launched intensive development efforts to ensure the automotive industry of the best possible materials to meet the necessary performance criteria. This paper discusses the performance requirements for reinforced urethane body panels, and extrapolates back to the characteristics of the unfilled base urethanes necessary to meet these requirements. The raw material supplier uses characteristics of the unfilled polyurethane as guidelines in formulation work. These guidelines must be well-defined to facilitate the development of even more effective urethanes for exterior automotive body components in the future.