A surgical instrument useful for laparoscopic surgery comprising an insulated shaft, a control means and a connection to an electrosurgical radiofrequency power source, its distal end being of general J-hook form having a tissue-engaging ledge, and the shaft supporting a tissue-engaging clamping or cutting member movable toward the ledge in response to the control means so that an artery or other tissue in the pocket of the J-hook can be clamped or cut while radiofrequency current is applied. Instrument constructions disclosed incorporate one or two clamping members and a cutting member arranged such that with actuation, the clamping member(s) engages the ledge before the cutting member, and, by selective actuation of the electrosurgical power source, coagulation current can be applied while clamping an artery or other tissue against the ledge to stop flow of blood, and by further actuation of the control and suitable current to the cutting member, the artery or tissue may be cut. Selector means enable movement of one and prevent movement of one of the members during actuation; bipolar or monopolar energization is employed; the relatively long leg of the J-member has portals. Communicating through a lumen in the shaft for infusion or aspiration of fluid; the distal end surface of the J-hook defines a cutting edge for blunt dissection; and the control means comprises a single actuatable member by actuator rods for sealing clamp and cutting members, while a compression spring associated with the actuating rod of the sealing clamp member compresses when the clamp member is stopped, in clamping action upon the artery or tissue while cutting of tissue thereafter proceeds. A diamond film on tissue-engaging surfaces of a clamp, grasping or cutting surgical instrument improves heat transfer between tissue and instrument.