An energy delivery system for delivering electrical energy to tissue (10, 110, 302, 2000), the energy delivery system comprising: an elongate catheter member (12, 26, 126, 2006) defining a longitudinal axis and dimensioned for passage within a body vessel; and an expandable treatment member (14, 114, 2008) mounted to the catheter member, the treatment member including: an inflatable element (16, 116, 216, 316, 2036, 2200, 2206, 2300, 2400) adapted to transition between an initial condition and an at least partially expanded condition upon introduction of an irrigation fluid within the inflatable element; an electrode (19, 118, 832, 842, 2038, 2220, 2310, 2408, 2508, 2612, 2714) for delivering electrical energy to at least nerve tissue associated with the body vessel to cause at least partial denervation thereof; and at least one aperture (38, 138, 238, 330, 717, 330, 2042, 2218, 2306, 2414, 2520, 2716) dimensioned to permit passage of the irrigation fluid from the inflatable element to contact the body vessel whereby the solution enters a wall of the body vessel; wherein the at least one aperture is dimensioned to deliver the irrigation fluid at a pressure sufficient to facilitate passage of the irrigation fluid at least within the wall of the body vessel; wherein the apertures are each dimensioned to deliver the irrigation fluid at a pressure ranging from about 1 atm to about 4 atm; wherein the catheter member defines a fluid lumen (2012, 2015, 2412) for delivering the irrigation fluid to the inflatable elementof the treatment member; the system further comprising a source of irrigation fluid in fluid communication with the fluid lumen of the catheter member and the inflatable element of the treatment member; the system further comprising a pump (330, 331, 2028) couplable to the fluid lumen of the catheter member, the pump dimensioned to deliver the irrigation fluid from the source to the fluid lumen of the catheter member at a pump pressure sufficient to convey the irrigation fluid through the fluid lumen and out the apertures at the pressure to enhance passage of the irrigation fluid at least within the wall of the body vessel; the system including a sensor (129, 332, 333, 334, 811, 2034) in fluid communication with at least the fluid lumen of the catheter member; the system further comprising a controller (324, 2032) for controlling operation of the pump; wherein the controller includes logic responsive to a parameter detected by the sensor to vary operation of the pump. an elongate catheter member (12, 26, 126, 2006) defining a longitudinal axis and dimensioned for passage within a body vessel; and an expandable treatment member (14, 114, 2008) mounted to the catheter member, the treatment member including: an inflatable element (16, 116, 216, 316, 2036, 2200, 2206, 2300, 2400) adapted to transition between an initial condition and an at least partially expanded condition upon introduction of an irrigation fluid within the inflatable element; an electrode (19, 118, 832, 842, 2038, 2220, 2310, 2408, 2508, 2612, 2714) for delivering electrical energy to at least nerve tissue associated with the body vessel to cause at least partial denervation thereof; and at least one aperture (38, 138, 238, 330, 717, 330, 2042, 2218, 2306, 2414, 2520, 2716) dimensioned to permit passage of the irrigation fluid from the inflatable element to contact the body vessel whereby the solution enters a wall of the body vessel; wherein the at least one aperture is dimensioned to deliver the irrigation fluid at a pressure sufficient to facilitate passage of the irrigation fluid at least within the wall of the body vessel; wherein the apertures are each dimensioned to deliver the irrigation fluid at a pressure ranging from about 1 atm to about 4 atm; wherein the catheter member defines a fluid lumen (2012, 2015, 2412) for delivering the irrigation fluid to the inflatable elementof the treatment member; the system further comprising a source of irrigation fluid in fluid communication with the fluid lumen of the catheter member and the inflatable element of the treatment member; the system further comprising a pump (330, 331, 2028) couplable to the fluid lumen of the catheter member, the pump dimensioned to deliver the irrigation fluid from the source to the fluid lumen of the catheter member at a pump pressure sufficient to convey the irrigation fluid through the fluid lumen and out the apertures at the pressure to enhance passage of the irrigation fluid at least within the wall of the body vessel; the system including a sensor (129, 332, 333, 334, 811, 2034) in fluid communication with at least the fluid lumen of the catheter member; the system further comprising a controller (324, 2032) for controlling operation of the pump; wherein the controller includes logic responsive to a parameter detected by the sensor to vary operation of the pump.