Abstract: An improved catheter is provided that is particularly useful for simultaneously mapping electrical activity at multiple locations within the heart. The catheter comprises an elongated catheter body having proximal and distal ends and at least one lumen extending longitudinally therethrough. A control handle is attached to the proximal end of the catheter body. A mapping assembly is mounted to the distal end of the catheter body. The mapping assembly comprises at least two elongated flexible spines, each spine having a proximal end attached to the distal end of the catheter body and a free distal end. Each spine carries at least one electrode along its length. The catheter further comprises at least two spine puller wires, each spine puller wire corresponding to one of the at least two spines.