Roads are generally designed with a camber to facilitate drainage. Running on a cambered road has been suggested as a potential cause of injury. Two possible mechanisms are mediolateral control and impact shock. The purpose of this study was to investigate the effect of a cambered surface on rearfoot motion and impact shock. Twelve runners ran at 3.83 m/s on both a flat and a cambered surface with the left side raised for all of them. Selected rearfoot kinematic and tibial acceleration measures were evaluated using a 2 x 2 repeated-measures ANOVA. The touchdown angle was less supinated on the left (high) side than on the right (low) side on the cambered surface. Maximum pronation was greater on the left (high) high side than on the right (low) side, as was total rearfoot motion. Maximum velocity of pronation was greater under the left (high) limb than under the right (low) limb while running on the cambered road. Time to maximum pronation did not differ, nor were there differences in peak acceleration or time to peak acceleration. The results of this study suggest that running on a cambered road caused changes in rearfoot motion kinematics that may predispose an individual to injury. Also, since the impact shock did not change with changes in rearfoot motion, perhaps the role of pronation on shock attenuation should be reexamined.