An experimental study was performed to investigate the relationship between stress and peripheral nerve recovery. Male Wistar rats weighing 200-250 g were used. The sciatic nerve was crushed unilaterally with an aneurysm clip. Stress was applied by water immersion for 3 h, three times a week, from 1 week preoperatively, and continued for 6 or 8 weeks. The animals' walking tracks were measured every week to evaluate nerve function, and a sciatic functional index (SFI) was calculated. Specimens for histological examination were taken from the nerve at a site distal to the crush injury. By 3 weeks postoperatively, the SFI in the non-stress groups had recovered, but it remained at significantly lower levels in the stress groups (P < 0.01). Histological studies showed that the recovery of nerve fibers was retarded and regenerating axons were smaller in the stress groups. Peripheral nerve recovery after crush injury was suppressed by water-immersion stress.