Hemodilution therapy in patients with ischemic cerebrovascular disease has recently become increasingly controversial, since controlled prospective trials failed to prove unequivocal clinical effects. A general rejection of hemodilution, however, does not seem to be justified. Undoubtedly, there is a beneficial influence on some hemorheologically relevant parameters as well as on cerebral blood flow (CBF). In addition, there is no proof that subgroups of patients profiting from this kind of treatment do not exist. Hemodilution is not recommended for patients with cerebral hemorrhages or hemorrhagic infarctions. In cases with transient ischemic attacks or ischemic strokes, however, this treatment should be taken into consideration further on. The application of hemodilution therapy in patients with progressive strokes depends on clinical signs, the course, the CT scan result, and sonographical findings. Recently, hydroxyethyl-starch (HES) has increasingly been used as an hemodiluting agent. The application of Dextran 40 should be limited to young normotensive patients without cardiac or renal disease.