Exterior body panels made from reinforced reaction injection molded (RRIM) urethanes are showing considerable promise for the automotive industry as a means of making lighter weight parts having corrosion and damage resistance. RRIM urethanes offer many advantages over metal and competitive plastic materials for these applications. Market projections and encouraging developmental efforts by automotive companies indicate RRIM urethanes will be widely used in the automobile industry in the near future.Proper understanding of RRIM urethanes is essential as these materials are evaluated for specific exterior body panel applications. Factors influencing the successful utilization of RRIM urethanes are discussed as related to mold design, material processing, and physical properties of the materials. Successful ways to control these factors are discussed.