Impact is considered the most critical part of the stance phase for the development of chronic articular disorders such as osteoarthritis in the equine distal limb. Modern, synthetic shoeing materials are believed to modify impact and therefore are often used to treat and/or prevent lameness due to chronic joint disorders. Scientific evidence is scarce, however, to prove this. Hoof impact of forelimb was compared quantitatively in a group of horses under three conditions: unshod, classical steel shoes and shod with a synthetic shoe. Twelve sound warmblood horses were trotted by hand on an asphalt track at a mean speed of 3.5 m s 21 and measured in a Latin square design (unshod condition, with steel shoes and with polyurethane (PU) shoes) using a triaxial accelerometer that had been fixed to the lateral hoof wall of the left forelimb. The sampling frequency was set at 10 kHz per channel. The maximum amplitude of vertical and horizontal, forward/backward accelerations at hoof impact was lowest when shod using the PU shoeing condition (P , 0.05), but the duration of the impact vibrations was lowest when unshod. PU shoes cause more damping, less friction and slower shock absorption at hoof level compared with the other two conditions and thus modify impact. Synthetic, polyurethane shoes may help in reducing peak vibrations. These short-term effects appear to be promising enough to evaluate PU shoes under field conditions in reducing impact on the longer term after substantial wear and tear. Furthermore, the possible role of synthetic materials in repairing critical tissues or even in preventing osteoarthritis in horses warrants further investigation.