The mechanical factors in tendon repair have been studied and physical principles applied to this unsolved problem. A new technique of tendon repair has been derived and tested in the laboratory. Compared to several well known techniques it has been shown to have three times the tensile strength and to allow one tenth the gap to form between the tendon ends under load. It has been designed not to constrict the blood supply of the tendon and the tests indicate that it will be strong enough to allow early active mobilisation even after inflammation has caused the tendon to soften.