Four stable chronic haemodialysis patients were studied during two periods of 3 weeks: at first a 'standard' haemodialysis (S/HD) was used, followed by 'computer-modulated' haemodialysis (CM/HD). We used a monitor Hospal Monitral-S with Hospal DPM (Display Programmer Module) that allows the programming of 'weight loss rate' and 'dialysate osmolality'. During standard haemodialysis fluid was removed at a constant rate of 1 kg/h with constant sodium dialysate of 143 mmol/l. During computer-modulated haemodialysis the dialysate sodium concentration and the fluid removal of 4 kg per session was modulated by display programmer module.