There is still a controversy on the treatment of the incomplete tear of tendons.Some authors insist to suture up, and some prefer not to suture. An animal experiment was performed for this purpose. One hundred twenty tendons of chicken feet were cut transverse and oblique cuts in equal number incompletely into 25%, 50% and 75%, respectively. Sixty tendons on the left feet were sutured up with external P.P. immobilization for 3 weeks while the other 60 tendons on the right feet were not sutured but with simple dressing only. The postoperative results assessed by various methods from functional observation and histological sectionsshowed that the suture group with external immobilization had a definitely superior result than that of the nonsuture group. The tendon cut over 50% was worse than those less than 50%. There was no much difference between whether the cut was transverse or oblique.