The purpose of this study was to evaluate the effects that operative mobilization and transposition of the ulnar nerve have on both neural excursion and mechanical properties. Twelve dogs underwent ulnar nerve transposition and postoperative casting. Four animals were killed at 3 weeks and four animals were killed at 6 weeks. Four animals had their casts removed at 3 weeks, were allowed to ambulate, and were killed at 6 weeks. Operated and contralateral control nerves were compared. Neural excursion was measured near the elbow and 12 cm proximally. The nerves were harvested and their mechanical properties determined. Repeated measures analysis of variance revealed significant differences in longitudinal excursion between control and experimental groups at both sites. Ultimate strain, ultimate strength, and modulus were significantly reduced in the experimental groups. No differences were seen in cross-sectional area or stiffness between control and experimental groups. Analysis revealed no independent effect of the rehabilitation method. Results of this study indicate that significant changes in neural excursion, ultimate strain, ultimate strength, and modulus occur following ulnar nerve mobilization and transposition and that these changes persist throughout the early postoperative period.