Abstract: A tissue ablation system includes an elongated shaft, such as a surgical probe shaft, and an needle electrode array mounted to the distal end of the shaft, and an ablation source, such as, e.g., a radio frequency (RF) generator, for providing ablation energy to the electrode array. The tissue ablation system further includes a heat sink disposed within the distal end of the shaft in thermal communication with the needle electrode array. In this manner, thermal energy is drawn away from the needle electrode array, thereby cooling the electrode array and providing a more efficient ablation process. The tissue ablation system further comprises a coolant flow conduit in fluid communication with the heat sink, so that the thermal energy can be drawn away from the heat sink. In the preferred embodiment, the flow conduit includes a thermal exchange cavity in fluid communication with the heat sink, a cooling lumen for conveying a cooled medium (such as, e.g.