Exposure to complement-activating cellulosic dialysis membranes has been claimed to adversely affect the course of acute renal failure (ARF). To test this hypothesis, male Sprague-Dawley rats were allocated to 2 groups: in Group 1, ARF was induced by bilateral renal artery clamping whereas in Group 2, animals underwent a sham procedure. In each group, rats were further allocated to undergo hemodialysis with either a Cuprophan, a Hemophan, or a polyacrylonitrile minidialyzer on Days 4 and 8 after surgery, or no dialysis. Renal function was measured by inulin clearance on the days after dialysis. Additionally, total complement activity (CH50) was estimated on Days 1, 2, 4, and 8, and complement factor C3 was detected immunohistochemically. The degree of renal failure and the rate of recovery of renal function were similar in all the ARF groups irrespective of whether they had undergone dialysis or not, or of the type of the dialysis membrane. Furthermore, there were no significant differences in the course of CH50 or in the amount and distribution of complement factor C3 in the kidney tissue between the rats of Groups 1 and 2. Our findings refute the hypothesis that in ischemic ARF exposure to complement-activating cellulosic dialysis membranes impairs the recovery of renal function in rats.