Background: Tendo Achillis lengthening is performed by means of Z-plasty in the classic treatment of clubfoot. In the Ponseti method for treating clubfoot, Achilles tenotomy is performed percutaneously for residual equine deformity. A randomized study was designed to compare tendon healing after tenotomy versus Z-plasty. Methods: Thirty-six Sprague-Dawley rats were divided randomly into two groups. On the first day, while the right tendo Achillis of group 1 rats underwent tenotomy, those of group 2 rats underwent Z-plasty. Nine rats from each group were humanely killed on days 21 and 45 postoperatively. The two groups were compared with each other biomechanically and histologically. The Achilles tendons of eight rats in each group were evaluated biomechanically, and the remaining rat in each group underwent histologic evaluation. Results: Mean ± SD maximum load at rupture of the treated tendons on days 21 and 45 in the tenotomy group was 26.38 ± 7.31 N and 47.16 ± 15.36 N, respectively, and in the Z-plasty group was 27.37 ± 5.20 N and 45.27 ± 9.59 N, respectively. The biomechanical evaluation revealed no significant difference in terms of breaking forces between the two groups. The difference between breaking forces on days 21 and 45 was statistically significant for both groups. Conclusions: Tendons in the tenotomy group healed as well as those in the Z-plasty group, and Achilles tenotomy in the rat was similar to Z-plasty for Achilles tendon lengthening. Human correlation may or may not exist, but this study suggests that it should be considered and investigated. (J Am Podiatr Med Assoc 99(3): 216–222, 2009)