A wearable and, ultimately, an implantable artificial kidney is a long-held aim in the treatment of patients with end-stage renal disease, provided that it would combine continuous blood purification, preventing the fluctuations in the internal environment associated with hemodialysis, while maintaining a high efficiency for removal of uremic toxins. Sorbent and enzyme technology, allowing for the regeneration of dialysis fluid, have played a vital role in the development of present prototypes, although the development of a low-weight regeneration module as well as safety and control issues still need to be solved. Whereas the first human trials with a wearable device have been successfully conducted, there are still many hurdles to overcome before wearable dialysis can be routinely implemented in dialysis practice. Important in this respect are the absence of a safe continuous blood access system and the risk balance between anticoagulation and clotting and regulatory aspects.