Of the approximately 10 million people in the US living with paralysis, 15,000 are the result of spinal cord injury each year. The first year of car can range from $322,000-$986,000, with lifetime costs of $1.4-4M for someone injured at 25 years of age. In addition to potentially devastating sensorimotor disturbances, there is a huge financial cost, estimated to be $13.55B in medical care, therapy, and lost productivity nationwide. Until very recently, the recovery from spinal cord injury (SCI) was bleak, with little hope of restoring motor function. To address this we have demonstrated that the physiological state of the spinal circuitry of rats and cats can be modulated with epidural stimulation to generate voluntary limb motor function over a range of speeds, loads, and directions, a finding we have extended to humans. Three years post-injury, a motor complete spinal cord injured human subject was implanted with an epidural electrode array over the lumbosacral spinal cord. In less than one month after implantation, the subject could stand independently, and after 7 months of daily epidural stimulation and motor training, voluntary control of both legs was evident in the presence of epidural stimulation, whereas complete paralysis remained in absence of epidural stimulation. We will advance these discoveries with the use of non-invasive stimulation of the cervical cord to improve arm and hand function following SCI. Central to this proposal is our discovery of a painless electrical single-channel (stimulation of one part of the spinal cord) and dual-channel (stimulation of two different parts of the cord) paradigm that can be applied to the surface of the skin, termed transcutaneous electrical stimulation (TES), bypassing the need for a surgically-implanted electrode array. In the first phase of this proposal we will demonstrate proof-of-principle that stimulation of the cervical spinal cord can improve motor function by: 1) Testing responses to transcutaneous electrical stimulation in subjects with spinal cord injury; and 2) defining the operational parameters of electrical stimulation that that are most effective using a machine-learning protocol, and 3) produce a dual-channel commercial prototype. This commercial product will undergo testing similar to the proof- of-principle device. This device will then be tested in subjects with cervical spinal cord injury and evaluated with a machine-learning protocol. This Phase I proposal will deliver a device that can painlessly and non-invasively aid in the recovery of SCI by delivering a specific electrical stimulation paradigm to the cervical cord that improves use of the arms and hands.