We examined recovery of claw size and function following autotomy in red rock crabs Cancer productus. We also tested for costs of regeneration to growth and documented the frequency of claw injury in C. productus populations in Barkley Sound, Canada. Field and laboratory results indicated that crabs required at least three molts to recover a full-length cheliped. For injured crabs, regenerating claws were significantly less powerful than contralateral, normal (i.e., uninjured) claws even two instars after autotomy. Greater mechanical advantage in normal claws of injured (versus uninjured) crabs, however, suggests some morphological response by the remaining normal claw to increased exercise. Despite this compensatory response, our experiments indicate that injured crabs remain at a significant disadvantage while foraging. After adjusting for differences in propodus length, both regenerating and normal claws of injured crabs delivered significantly lower crushing forces than did claws of intact crabs. Energetic costs, in the form of reduced body size increase at the molt, were detected only for crabs regenerating both claws. High incidences of single claw loss in C. productus in Barkley Sound, together with our experimental data, suggest that much of the population experiences a prolonged foraging handicap following injury.