OBJECTIVE: To evaluate the management of sheath after repair of double tendons in clean-cut injury or severe injury in zone II d. METHODS: Forty-eight white leghorn chickens were divided into 4 groups. Both FDS and FDP tendons in zone II d of long toes were repaired with modified Kessler suture after tendon transection in group A (clean-cut tendon injury, sheath closure), group B (clean-cut tendon injury, sheath excision), group C (severe tendon injury, sheath closure) and group D (severe tendon injury, sheath excision), respectively. Biomechanical studies of gliding excursion and work of flexion were carried out 6 weeks and 12 weeks after tendon repair. The extent of adhesion was examined. RESULTS: After 6 and 12 weeks of repair, there were no significant differences in tendon excursion and work of flexion of the toes between groups A and B. Excursions of FDP tendons in group D was significantly larger than that in group C (P lt; 0.05). Work of flexion and extent of adhesion in group D was significantly less than that in group C (P lt; 0.05). CONCLUSION: The above results indicate that sheath can be closed after repair of both FDS and FDP tendons in clean-cut injury and that sheath should be excised in severe injury in zone II d.