An electrosurgical instrument capable of simultaneously ablating an area of tissue with microwave energy and performing resection with radiofrequency (RF) energy. The instrument comprises an energy conveying cable 100 which terminates in a dialectic tip 118. The energy conveying cable comprises a coaxial transmission line for conveying at least microwave energy, the coaxial transmission line comprising an inner conductive layer 104, an outer conductive layer 106 and a dielectric 108 separating the two. In one arrangement the inner conductive layer is formed around a hollow longitudinal passage 102 along, and preferably through, which an RF transmission line 110 extends. In this arrangement both the inner and outer conductors extend into the tip, with the inner conductor extending beyond the end of the outer conductor to form a microwave radiator. Active 126 and return 124 electrodes are also mounted on the tip and connected to the RF transmission line. In one particular arrangement the instrument provides a ball-shaped tip 200 comprising two conductive hemispheres 202, 204 separated by a planar dielectric layer 206, wherein the hemispheres are configured to both radiate microwave energy as a spherical field and provide respective active and return electrodes for delivering the RF energy.
