Summary Summary: Findings concerning the effects of colloids on haemostasis in critically ill patients are scarce. The results of studies in volunteers, after perioperative haemodilution as well as in-vitro results suggest that all colloids used for fluid resuscitation influence haemostasis by dilution of blood coagulation factors and blood cells. Dextran and gelatine solutions exert specific effects on thrombocyte function and quality of clot formation respectively. Their use in critical illness remains poorly documented. According to the clinical and laboratory data available, hydroxyethyl starch (HES) solutions with a mean molecular weight <200.000, a degree of substitution < 0.6, and a C2/C6 hydroxyethylation ratio > 6 exert little effects on haemostasis and can be used safely up to a dose of 2 g/kg b.w./d.