In dog experiments the surgical treatment of flexor tendons is discussed by the authors: the lesions of the tendons have been repaired according to the method of Paneva-Holevitch, with biphasic flexor tendon plasty; and for the substitution of the injured tendon sheath and the peritendinous slipping surfaces freely transplanted, autologous vein has been used. In the preparations removed after 8 weeks both the macroscopic and microscopic examinations showed satisfactory vascularity of the vein used as tendon sheath and of the tendinous tissue, as well as normal tissue structure. Between the vein and the tendon only small, ligamentous adhesions developed. On the basis of the good results obtained in experimental examinations the method is applied by the authors also in men with satisfactory result.