The adsorption method for regeneration of dialysate was introduced as a new principle in hemodialysis. To compare the efficacy of the Redy-system (regenerative dialysis supply system) which utilizes a sorbent cartridge, with the common single-pass systems, 2 patients were dialyzed weekly twice or three times 6 hours over a period of 3 months. Three different types of dialyzers were used: Cordis hollow-fiber, plate dialyzer Lundia Nova 17,0 mu and coil dialyzer Travenol Ultraflo II. Monitoring of serum nitrogen constituents (urea, creatinine, uric acid) showed that the efficacy especially of the hollow-fiber dialyzer was comparable with the single-pass-system. Serial measurements of electrolytes in dialysate and serum, as well as dialysate osmolarity and ammonia indicated that the adsorption method is a safe technique. The advantage of the Redy-system is its independency of a fixed and treated water supply system, since it is able to operate with 5.5 1 tap water, an electrolyte concentrate being added in the recirculation system. Therefore this dialysis device can be installed everywhere, giving the dialysis patient more independency.