Daily dialysis has shown excellent clinical results because a higher frequency of dialysis is more physiologic. On-line hemodiafiltration (OL-HDF) is a HDF technique that combines diffusion with high convection in which the dialysis fluid itself is used as a reinfusion solution. The aim of this study was to demonstrate the beneficial effect of the more effective dialysis schedule (daily dialysis) with the dialysis modality that offers the highest uremic toxin removal (on-line HDF). Eight patients, six males and two females, on standard 4 to 5 hours three times a week OL-HDF (S-OL-HDF) were switched to daily OL-HDF (D-OL-HDF) 2 to 21/2 hours six times per week. Dialysis parameters were identical during both periods and only frequency and dialysis time of each session were changed. Tolerance, uremic toxin removal, urea kinetics, biochemical and anemia profiles, blood pressure, and left ventricular hypertrophy were evaluated. D-OL-HDF was well accepted and tolerated. The disappearance of postdialysis fatigue was rapidly reported by patients. Patients mantained the same [time average concentration (TAC) and weekly single-pool Kt/V (spKt/V)] throughout the study. However, equivalent renal urea clearance (EKR), standard Kt/V and weekly urea reduction ratio (URR) were increased during D-OL-HDF. Weekly urea, creatinine, osteocalcin, beta2-microglobulin, myoglobin, and prolactin reduction ratios were improved with D-OL-HDF. There was a significant decrease in predialysis plasma levels of urea, creatinine, acid uric, beta2-microglobulin and homocysteine over 6 months. Phosphate binders were reduced and antihypertensive drugs were stopped. A 30% regression of left ventricular mass was observed. The change from S-OL-HDF to D-OL-HDF was well tolerated. Disappearance of postdialysis fatigue, better dialysis adequacy, a higher removal of middle and large molecules, a reduction of phosphate binders, improvement of status nutritional, and an important reduction of cardiovascular risk factors were observed.