A bipolar electrosurgical instrument comprising jaws 13, 14 provided with a cutting electrode (16, Fig 1) and at least two coagulating/sealing electrodes and a closure detecting means preferably in the form of pressure sensors, strain gauges 75A-D, or distance gauges (76, Fig 12A) - for detecting whether the jaws 13, 14 are in their open or closed position. The device also comprises first and second switches (40, 43 Fig 6) to supply different RF waveforms to the electrodes. Actuation of the first switch effects the supply of a first, preferably coagulating, waveform whereas the waveform supplied by the second switch is dependent upon the position of the jaws 13, 14. If the detecting means 75, 76 indicate that the jaws 13, 14 have not been moved from their closed position since the first switch was activated then the waveform supplied by the second switch is a second, preferably cutting waveform. Whereas if when the second switch is activated, the detecting means indicate that the jaws 13, 14 have been moved between their closed and open positions since the first switch was activated then the waveform supplied is a third, preferably blended cutting and coagulating, waveform.
