An ultrasonic clamp coagulator assembly that is configured to permit selective cutting, coagulation and clamping of tissue during surgical procedures. An elongated portion of the instrument can be configured for endoscopic applications and has an outside diameter of less than 6 mm. The construction includes a clamping mechanism, including a clamp arm pivotally mounted at the distal portion of the instrument, which is specifically configured to create a desired level of tissue clamping forces, exceeding 4 pounds when the trigger is fully closed. The clamping mechanism includes a two-piece pad design and pad material that enables the higher tissue clamping forces and a force-limiting mechanism that effectively smooths out abusive tissue forces. The assembly also features hand activation configured to provide an ergonomical grip and operation for the surgeon. Hand switches are placed in the range of the natural swing of the surgeon's thumb, whether gripping the surgical instrument right-handed or left handed.