End stage kidney disease (ESKD) afflicts almost 808,000. Dialysis, the only currently available treatment except for a kidney transplant, is one of the most expensive items in the Medicare budget. Patients on dialysis have a poor quality of life and high mortality rates. Spending hours tethered to dialysis machines in clinics, the patients’ daily activities and social interactions are greatly restricted. Current dialysis treatment delivers an average of 12 weekly hours of blood filtration – significantly less than the weekly 168 hours of filtration provided by healthy native kidneys. The limited blood filtration leads to inadequate control of intravascular volume, insufficient removal of uremic toxins and failure to maintain electrolyte homeostasis – all resulting in poor clinical outcomes. Wearable Artificial Organs (WAO), a California based small business, has developed a miniaturized Wearable Artificial Kidney (WAK) that closely mimics the function of healthy native kidneys, and is worn on the patient's body allowing complete mobility during dialysis. Earlier versions of the WAK have been tested in bench, animal, and human studies in major centers around the globe, proving the concept's feasibility. While most of the targeted biological outcomes were met and patients responded positively, the prototypes used in the trials were too heavy and bulky to satisfy the requirements expressed by dialysis patients. As per patient's preferences, a smaller, discrete, and lighter WAK has been developed. The WAK3 system will be comprised of two devices: 1. a wearable, battery powered, dialysis device, weighing approximately 2 lbs. that uses a double channel opposite phase pulsatile pump, a dialyzer and a charcoal sorbent cartridge. This device will remove uremic toxins, salts and excess water; and 2. a stationary device containing additional sorbents to remove urea and phosphorus. The stationary device will connect only to the dialysis circuit of the wearable device, not the blood circuit. This device will operate while the patient is at rest and the wearable device’s batteries are recharging. This is a key innovation in the field. In Aim 1, a clinical trial will be carried out in 10 ESKD patients who will dialyze with the WAK3 for 2 days at the Brigham and Women's Hospital and then 5 days at home. In Aim 2, a pivotal clinical trial will be conducted. At Brigham and Women’s Hospital, 15 patients will be dialyzed with the WAK3 homes for 21 days. These trials will establish that the WAK3 can safely and efficiently deliver superior clinical outcomes and improved quality of life at reduced costs. Upon completion, this project will provide the FDA with the data needed to approve a PMA application to go to market.