Various consensus groups convened in recent years to discuss plasma volume expansion solutions have suggested limiting the use of human albumin because of its high cost and have favored synthetic crystalloids or colloids for most clinical settings. Dextrans are colloids that are not widely used in most Europeans countries. Gelatins, in spite of the fact that unlimited amounts can be used, produce only moderate volume expansion and can trigger allergic reactions. The availability in Spain of hydroxyethylstarches (HES), a new type of colloid, may significantly change volume replacement strategy. HES are modified natural polymers. Three types, with different initial molecular weights, are used in Europe: high molecular weight HES, whose use in increasingly rare; low molecular weight HES (Expafusin), whose effect is short-lived; and medium molecular weight HES (Elohes, Fresenius-Laboratories Mein), which have recently been registered in Spain. Studies have shown that Elohes 6% (6% HES 200/0.62) provides volume expansion comparable to that of human albumin in clinical settings (cardiac surgery, shock, burns, etc.). The side effects of HES are usually minor. The frequency of anaphylactoid reactions is low, similar to that associated with human albumin. The effects on coagulation depend on molecular weight and duration of HES administration. Only in studies of hemodilution lasting 10 days with 6% HES 200/0.62 has VIII/von Willebrand complex been shown to decrease. If the recommended daily dose of this HES is respected, however, coagulation disorders are minimal. The effect of HES on kidney function is at present a subject of controversy. Thus, thanks to its prolonged effect on volume and few side effects, medium molecular weight HES colloids are the ones most often recommended for use in anesthesia and postoperative intensive care.