2 types of infusion solutions are used for volume replacement: crystalline fluids (such as NaCl 0.9% and lactated Ringer's solution) and colloidal fluids made of hydroxyethyl cellulose, albumin or gelatine. The choice of fluids used appears to be determined by the personal preference of the physician or the department. Infusion of colloidal solutions results in rapid recovery of the circulating volume but can cause anaphylaxis, renal insufficiency and an increased bleeding tendency. The use of hydroxyethyl cellulose (HEC) is associated with higher mortality and renal impairment, and is therefore not very justifiable. Albumin-based infusions appear to be predominantly indicated for septic patients with hypoalbuminaemia. Gelatin-based infusion fluids have not yet been extensively studied. The balanced lactated Ringer's solution, the composition of which is closer to plasma than that of NaCl 0.9%, is being used with ever-increasing frequency. Lactated Ringer's infusion solution does not cause hyperchloremic acidosis and probably less often leads to renal insufficiency than when NaCl 0.9% is infused.