The main reason for using colloids as volume replacement is to maintain the circulating blood volume by stabilizing plasma oncotic pressure in the preoperative period. The effects of colloids on haemostasis potentially cause an alteration of the haemostatic mechanisms such as interference with platelet functions. Thus the side effects of colloids may be relevant clinically. The aim of this study is to clarify the clinical effects of colloids on blood coagulation and platelet functions.