The syndrome of sepsis-associated severe acute renal failure is a fre-quent component of sepsis-induced multiorgan failure. Continuous hemofiltration techniques are often used in its dialytic management but little is known about their impact. The aim of this study is to define the biochemical and clinical impact of continuous hemodiafiltration (CHD) in the management of this syndrome and to retrospectively compare it to that of conventional dialysis. A prospective, cohort study and retrospective comparison with historical controls was conducted at an intensive care unit (ICU) of a tertiary institution. Eighty-seven consecutive septic pa-tients with acute renal failure were treated by continuous hemodiafil-tration and 40 consecutive similar patients by conventional dialysis. All new cases of severe acute renal failure with sepsis were treated by means of continuous hemodiafil-tration. Historical controls were treated by means of conventional dialysis. Illness and sepsis severity were assessed on admission and prior to initiation of teatment. Bio-chemical variables were assessed daily. Outcome was measured as discharge from the ICU, duration of oliguria and discharge from hos-pital. Of the 87 patients treated by hemodiafiltration, 86 had multior-gan failure, 71 (81.6%) septic shock and 52 (59.8%) bacteremia/fun- gemia. Their APACHE II score on admission was 29.9 and their mean organ failure score prior to treat-ment was 4.3. Hemodiafiltration resulted in a significant fall in mean urea and creatinine levels within 24 h and in the correction of acidosis. The mean alveolar-arterial gradient fell from 276 to 211 mm Hg (p < 0.02) within 24 h of therapy. Complications were few and mostly related to vascular access. Hemodynamic stability was main-tained throughout all of the 18,122 h of treatment. Thirty-one (35.6%) patients survived to hospital discharge. Comparison with conventionally treated historical controls showed better control of uremia at 24 h. Among patients with an APACHE II score <30, survival was greater with hemodiafiltration (51.2 vs. 26.6%; p < 0.05). This was also true for patients with 4 or fewer failing organs (53.1 vs. 26.9%; p < 0.05). Continuous hemodiafiltration achieves rapid and reliable control of uremia and acidosis in spesis-associat- ed severe acute renal failure and is associated with improved gas ex-change. Survival in these extremely ill patients approached 35%. The use of hemodiafiltration is associ-ated with better early control of uremia than with conventional he-modialysis or peritoneal dialysis. In some patient subgroups, continuous hemodiafiltration also appears to provide a survival advantage. The above findings suggest that continuous hemodiafiltration may be a form of renal replacement therapy ideally suited to the man-agement of sepsis-associated severe acute renal failure.