A renal neuromodulation system for treatment of a human patient, the system comprising: a procedural guide wire , a catheter including an elongate shaft having a proximal end and a distal end , wherein the distal end of the shaft is configured for intravascular delivery over the procedural guide wire to a renal artery of the patient; a pre-shaped tubular spiral structure disposed at or proximate to the distal end of the elongate shaft , wherein the spiral structure is configured to transform between an unexpanded configuration and an expanded configuration that tends to assume the shape of the pre-shaped spiral structure , and wherein the spiral structure is composed, at least in part, of multifilar stranded nitinol wire; a plurality of electrodes associated with the spiral structure , wherein the elongate shaft and the spiral structure together define a guide wire lumen therethrough, and wherein the guide wire lumen is configured to slidably receive the procedural guide wire to locate the spiral structure at a target treatment site within a renal blood vessel of the patient and to restrain the spiral structure in the unexpanded configuration, and wherein proximal movement of the procedural guide wire through the guide wire lumen relative to the spiral structure such that a distal end portion of the guide wire is at least partially within the guide wire lumen transforms the spiral structure to the expanded configuration, wherein the procedural guide wire comprises a distal portion having varying flexibility along its length so as to provide increased flexibility distally, characterised in that the spiral structure provides a shape-recovery force sufficient to overcome the straightening force provided by the distalmost portion of the guide wire. a procedural guide wire , a catheter including an elongate shaft having a proximal end and a distal end , wherein the distal end of the shaft is configured for intravascular delivery over the procedural guide wire to a renal artery of the patient; a pre-shaped tubular spiral structure disposed at or proximate to the distal end of the elongate shaft , wherein the spiral structure is configured to transform between an unexpanded configuration and an expanded configuration that tends to assume the shape of the pre-shaped spiral structure , and wherein the spiral structure is composed, at least in part, of multifilar stranded nitinol wire; a plurality of electrodes associated with the spiral structure , wherein the elongate shaft and the spiral structure together define a guide wire lumen therethrough, and wherein the guide wire lumen is configured to slidably receive the procedural guide wire to locate the spiral structure at a target treatment site within a renal blood vessel of the patient and to restrain the spiral structure in the unexpanded configuration, and wherein proximal movement of the procedural guide wire through the guide wire lumen relative to the spiral structure such that a distal end portion of the guide wire is at least partially within the guide wire lumen transforms the spiral structure to the expanded configuration, wherein the procedural guide wire comprises a distal portion having varying flexibility along its length so as to provide increased flexibility distally, characterised in that the spiral structure provides a shape-recovery force sufficient to overcome the straightening force provided by the distalmost portion of the guide wire. <EOS>