A surgical instrument for cutting and coagulating tissue is provided that includes an elongate sheath and an ultrasonic blade. In one embodiment, an ultrasonic blade is positioned within a sheath such that movement of the sheath relative to the blade results in the dissection and/or coagulation of tissue therebetween. In another embodiment, an ultrasonic blade is positioned within a sheath such that movement of the blade relative to the sheath results in the dissection and/or coagulation of tissue therebetween. The size and shape of distal ends of the blade and sheath determine the size and shape of the tissue being cut and/or removed from a body.