An ultrasonic clamp coagulator apparatus comprising: a housing, said housing comprising an actuator; an outer tube having a proximal end joined to said housing, and a distal end, said outer tube defining a longitudinal axis; an actuating element reciprocably positioned within said outer tube, said actuating element operatively connected to said actuator; an ultrasonic waveguide positioned within said outer tube, said ultrasonic waveguide having a curved end-effector defining a vertical plane of asymmetry extending distally from said distal end of said outer tube, wherein said end-effector comprises a broad edge and a narrow edge, wherein said narrow edge is defined by the intersection of a first surface and a second surface, wherein said first surface is concave and said second surface is convex and wherein said first surface extends from the distal end proximally into said end-effector defining a length of said first surface; and a clamp arm pivotally mounted on said distal end of said outer tube for pivotal movement with respect to said end-effector for clamping tissue between said clamp arm and said end-effector, said pivotal movement occurring about a horizontal axis, the arc of said pivotal movement of said clamp arm defined in said vertical plane, said vertical plane having a vertical axis orthogonal to both said longitudinal axis and said horizontal axis, said clamp arm operatively connected to said actuating element so that reciprocal movement of said actuating element pivots said clamp arm along said vertical plane; wherein said broad edge is radiused and blunt, for providing a broad edge for clamping tissues between it and the clamp arm, and said narrow edge is for unclamped cutting; wherein said length of said first surface is selected to balance said waveguide by providing a functional asymmetry such that excursion proximal to said functional asymmetry of said end-effector along said vertical axis is limited to less than 15%. a housing, said housing comprising an actuator; an outer tube having a proximal end joined to said housing, and a distal end, said outer tube defining a longitudinal axis; an actuating element reciprocably positioned within said outer tube, said actuating element operatively connected to said actuator; an ultrasonic waveguide positioned within said outer tube, said ultrasonic waveguide having a curved end-effector defining a vertical plane of asymmetry extending distally from said distal end of said outer tube, wherein said end-effector comprises a broad edge and a narrow edge, wherein said narrow edge is defined by the intersection of a first surface and a second surface, wherein said first surface is concave and said second surface is convex and wherein said first surface extends from the distal end proximally into said end-effector defining a length of said first surface; and a clamp arm pivotally mounted on said distal end of said outer tube for pivotal movement with respect to said end-effector for clamping tissue between said clamp arm and said end-effector, said pivotal movement occurring about a horizontal axis, the arc of said pivotal movement of said clamp arm defined in said vertical plane, said vertical plane having a vertical axis orthogonal to both said longitudinal axis and said horizontal axis, said clamp arm operatively connected to said actuating element so that reciprocal movement of said actuating element pivots said clamp arm along said vertical plane; wherein said broad edge is radiused and blunt, for providing a broad edge for clamping tissues between it and the clamp arm, and said narrow edge is for unclamped cutting; wherein said length of said first surface is selected to balance said waveguide by providing a functional asymmetry such that excursion proximal to said functional asymmetry of said end-effector along said vertical axis is limited to less than 15%.