An electrosurgical instrument with a movable fluid delivery sheath assembly for variable fluid supply during surgical procedures is disclosed. The instrument comprises at least one active electrode and at least one return electrode, positioned on the instrument distal end. The sheath assembly has an outer sheath that is external to the instrument shaft, to provide a lumen. The sheath assembly lumen is axially movable between first and second positions relative to a fluid delivery element, for varying target site treatment and fluid delivery. In the first position the shaft distal end is axially distal to a leading edge of the sheath assembly. In the second position the sheath assembly distal leading edge is positioned axially adjacent or distal to the end of the shaft. The fluid delivery element comprises an inner lumen extending through at least a portion of the shaft, and at least one port extending radially through the shaft. The port is in communication with the inner lumen. A fluid supply source provides fluid through the port, sheath lumen and inner lumen.
