Methods and devices for occluding a vessel during a percutaneous ablation procedure. An elongated access device having a lumen and a tissue piercing, open distal end in communication with the lumen is used to percutaneously access a vessel that supplied blood to the tissue to be treated. An elongated balloon deployment device is used to deliver a balloon into the interior of the vessel. The balloon is inflated, resulting in the occlusion of the vessel. The tissue to be treated is ablated. Because there is little or no blood to transfer the thermal energy away from the heated tissue, the ablation procedure is performed more efficiently. The balloon may be subsequently deflated allowing normal flow through the vessel to return.