Chronic pain remains a serious public health problem, resulting in approximately 100 million chronic pain patients in the U.S. alone [1]. While numerous treatments exist, none completely addresses this issue. In particular, spinal cord stimulation (SCS) has become an established technique for treating patients with chronic neuropathic pain [2]. The conventional paradigm for SCS treatment is to attempt to mask the pain by substituting the pain sensation with paresthesias [3]; however, newer studies have shown that it is possible to gain excellent pain relief without concomitant paresthesias ("sub-threshold stimulation") using different stimulation parameters [4] [5]. Because these paresthesia-free programming paradigms are still new, the best to place the stimulation and the best programming parameters to use is still unclear, making it difficult to place the leads during surgical implantation and to program the patient afterwards. Additionally, sub-threshold stimulation does not provide immediate pain relief, but may take several hours or even days to feel relief, making a simple programming session of a few hours insufficient to determine the optimal stimulation placement. While these differences from conventional SCS make programming more difficult initially, studying this new stimulation paradigm, especially differences in optimal stimulation location and the time course of pain relief, may also provide insight into the mechanism of action of sub-threshold stimulation. This protocol aims to study the optimal stimulation parameters and locations with SCS using sub-threshold stimulation.