Once hemodialysis had become established as a treatment for chronic kidney disease, the early pioneers realized the limitations of the treatment, particularly in terms of the impact intermittent thrice weekly hemodialysis had on a patient's quality of life-not only time spent on dialysis and time traveling to and from treatment, but also dietary and fluid restrictions. This led to the search for the holy grail--a wearable hemodialysis device (WAK), that would allow patients to receive continuous treatment, while going on with the normal activities of daily life. Such a device would not only provide adequate solute clearances and control both electrolyte and acid-base status, but also improve blood pressure control--all while allowing a liberal diet. Despite many attempts, to develop such a wearable artificial kidney, it is only recently, with the advent of microtechnologies, that it has been possible to construct a truly wearable device, which can accurately regulate ultrafiltration and achieve adequate solute clearances. One such device has recently completed successful human pilot studies, designed to test device reliability, safety, and efficacy.