The syndrome of sepsis-associated severe acute renal failure is a frequent 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 patients with acute renal failure were treated by continuous hemodiafiltration and 40 consecutive similar patients by conventional dialysis. All new cases of severe acute renal failure with sepsis were treated by means of continuous hemodiafiltration. Historical controls were treated by means of conventional dialysis. Illness and sepsis severity were assessed on admission and prior to initiation of treatment. Biochemical variables were assessed daily. Outcome was measured as discharge from the ICU, duration of oliguria and discharge from hospital. Of the 87 patients treated by hemodiafiltration, 86 had multiorgan failure, 71 (81.6%) septic shock and 52 (59.8%) bacteremia/fungemia. Their APACHE II score on admission was 29.9 and their mean organ failure score prior to treatment 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.(ABSTRACT TRUNCATED AT 250 WORDS)