Hemodialysis (HD) for critically ill patients with acute renal failure has been provided as intermittent hemodialysis (IHD) or continuous renal replacement therapy (CRRT). IHD is often complicated by hypotension and inadequate fluid removal, and CRRT by high cost of solutions and problems with anticoagulation. Sustained low-efficiency daily dialysis (SLED) has been suggested as an alternative treatment. This is an observational, prospective pilot study describing the introduction of SLED at our institution. We compared SLED (23 patients, 165 treatments) with CRRT (11 patients, 209 days), focusing on cost, anticoagulation, and small solute removal. SLED consisted of 8 h of HD 6 days a week, with blood flow of 200 ml/min, dialysate flows of 350 ml/min, and hemofiltration with 1 l of saline/h. CRRT patients were anticoagulated with either heparin or citrate, and SLED patients with either heparin or saline flushes. The weekly costs to the hospital were $1431 for SLED, $2607 for CRRT with heparin, and $3089 for CRRT with citrate. Sixty-five percent of SLED treatments were heparin-free; filter clotting occurred in 18% of heparin treatments and 29% of heparin-free treatments (NS). Weekly Kt/V was significantly higher for SLED (8.4+/-1.8) and time-averaged serum creatinine was lower; equivalent renal clearance (EKRjc) was 29+/-6 ml/min for SLED, similar to that for CRRT. In summary, SLED may be routinely performed without anticoagulation; it provides solute removal equivalent to CRRT at significantly lower cost.