Adequate volume replacement therapy is a mainstay of managing the critically ill. The ideal kind of volume replacement in this situation still remains a challenge. In spite of an immense number of contributions to this problem there is still no definite answer. The ideal volume replacement strategy should not only aim at maintaining stable systemic hemodynamics, organ perfusion and microcirculation should be guaranteed or even improved as well. Due to its excellent efficacy, hydroxyethylstarch (HES) preparations are widely used to treat hypovolemia. The different physico-chemical properties of the available HES solutions, however, should be taken into account. Anphylactoid reactions as well as negative effects on coagulation, kidney/liver function and on the immune system are frequently used arguments against the administration of HES, but they can virtually be neglected when using modern HES preparations to correct hypovolemia. There are, however, still open questions concerning the use of HES in children, pregnant patients, patients with altered kidney function and in burn patients.