A surgical instrument, comprising: a housing having an elongated shaft extending distally therefrom, the elongated shaft supporting an end effector for treating tissue; at least one tensile member (66, 68) extending at least partially through the elongated shaft, a distal end of the at least one tensile member operatively coupled to the end effector such that longitudinal motion in the at least one tensile member induces movement of the end effector; a drive mechanism operatively coupled to a proximal end of the at least one tensile member, the drive mechanism including an actuator operable to induce longitudinal motion in the at least one tensile member; and a tensioning mechanism configured to constantly impart a proximally directed force on the drive mechanism such that the proximally directed force is transmitted to the at least one tensile member, characterized in that the elongated shaft includes a proximal portion extending distally from the housing and a distal articulating portion extending distally from the proximal portion, the distal articulating portion defining at least one joint therein to permit the distal articulating portion to pivot with respect to the proximal portion of the elongated shaft, the at least one tensile member includes a pair of articulation cables (66, 68) operatively coupled to the end effector such that relative longitudinal movement between the articulation cables induces articulation of the end effector, the end effector includes a pair of jaw members (30, 32), the surgical instrument further includes a drive cable extending at least partially through the elongated shaft and operable to move at least one of the pair of jaw members between an open position wherein the pair of jaw members are substantially spaced from each other and a closed position wherein the pair of jaw members are closer together, and the proximally directed force of the tensioning mechanism is transmitted to the pair of articulation cables to maintain a constant tension on the pair of articulation cables despite any creep elongation of the pair of articulation cables. a housing having an elongated shaft extending distally therefrom, the elongated shaft supporting an end effector for treating tissue; at least one tensile member (66, 68) extending at least partially through the elongated shaft, a distal end of the at least one tensile member operatively coupled to the end effector such that longitudinal motion in the at least one tensile member induces movement of the end effector; a drive mechanism operatively coupled to a proximal end of the at least one tensile member, the drive mechanism including an actuator operable to induce longitudinal motion in the at least one tensile member; and a tensioning mechanism configured to constantly impart a proximally directed force on the drive mechanism such that the proximally directed force is transmitted to the at least one tensile member, characterized in that the elongated shaft includes a proximal portion extending distally from the housing and a distal articulating portion extending distally from the proximal portion, the distal articulating portion defining at least one joint therein to permit the distal articulating portion to pivot with respect to the proximal portion of the elongated shaft, the at least one tensile member includes a pair of articulation cables (66, 68) operatively coupled to the end effector such that relative longitudinal movement between the articulation cables induces articulation of the end effector, the end effector includes a pair of jaw members (30, 32), the surgical instrument further includes a drive cable extending at least partially through the elongated shaft and operable to move at least one of the pair of jaw members between an open position wherein the pair of jaw members are substantially spaced from each other and a closed position wherein the pair of jaw members are closer together, and the proximally directed force of the tensioning mechanism is transmitted to the pair of articulation cables to maintain a constant tension on the pair of articulation cables despite any creep elongation of the pair of articulation cables. the elongated shaft includes a proximal portion extending distally from the housing and a distal articulating portion extending distally from the proximal portion, the distal articulating portion defining at least one joint therein to permit the distal articulating portion to pivot with respect to the proximal portion of the elongated shaft, the at least one tensile member includes a pair of articulation cables (66, 68) operatively coupled to the end effector such that relative longitudinal movement between the articulation cables induces articulation of the end effector, the end effector includes a pair of jaw members (30, 32), the surgical instrument further includes a drive cable extending at least partially through the elongated shaft and operable to move at least one of the pair of jaw members between an open position wherein the pair of jaw members are substantially spaced from each other and a closed position wherein the pair of jaw members are closer together, and the proximally directed force of the tensioning mechanism is transmitted to the pair of articulation cables to maintain a constant tension on the pair of articulation cables despite any creep elongation of the pair of articulation cables.