The injured tendon is thought to be healed by, extrinsic healing from tendon sheath and adjacent connective tissue, and intrinsic healing from epitenon and endotenon. About the factors influencing the healing of injured tendon, many authors reported the effects of mobilization, electricity, ultrasound and various druge. Especially, active or passive mobilization had been known to promote the healing process and to reduce adhesion. To investigate the influences of active limited mobilization, intrinsic and extrinsic healing process, right Achilles tendons of 30 New Zealand white rabbits were grouped according to the types of treatments (Group I; tenotomy of Achilles tendon only, Group II; Tenotomy and long leg cast, Group III; surgical repair after tenotomy and long leg cast). The tendon sheath was repaired in all the groups, and the left Achilles tendons were used as control. At six weeks after operation, the tendons were removed and analysed biomechanically using Instron 1000, and histologically. The following results were obtained: 1. There were significant decreased of break strength, in order of Group III, Group I and Group II(p<0.05). But, no difference was found between control group and Group III. 2. Extension length to the rupture, was decreased significantly in the experimental groups than control group. But there was no difference among the experimental groups. 3. Histologically, dense proliferation of fibroblasts and hypertrophy of tendon was observed in Group I; and matured fibricytic tendon tissues in Group II and III. In Group II, the amount of matured tendon tissues and degree of maturity were less than in Group III. In summary, suture and active limited motion were considered as promoting factors on the tendon healing.