Two hundred eleven patients with acute ischemic stroke, stage III or IV, received daily intravenous infusion of 500-1000 mL low-molecular dextran (dextran 40) over a period of 4 days. In 10 cases (4.7%) acute renal failure, associated with dextran infusion, could be observed; oligoanuria occurred after a mean time of 4 (3-6) days. The incidence of dextran-induced acute renal failure was significantly higher in patients with a preexisting reduction of glomerular filtration rate below 30 mL/min/1.73 m2 (p < 0.005). Five of the patients (50%) with acute renal failure died within 4-12 days after the hemodilution therapy with dextran 40; this high lethality was due to nonrenal complications.