Volatile anaesthetics are often used during cardiopulmonary bypass (CPB). To understand the kinetics of inhaled anaesthetics during CPB, anaesthetists should understand changes in blood solubility caused by fluid use. We set out to predict the solubility of three volatile anaesthetics, desflurane. isoflurane and halothane, during CPB by determining; (i) their solubility in fresh whole blood and eight CPB priming fluids at 37℃; (ii) the effect of temperature on the solubility of these anaesthetics in lactated Ringer's, gelofusin, banked blood and plasma; (iii) their solubilith in different mbotures of these four priming fluids at different temperatures; and (iv) their estimated and actual solubility in blood during hypothermic CPB, We calculated solubilith using a concept of volume fraction partition coefficient and compared estimated and measured solubilities. For the three anaesthetics tested, solubilities are in the order. fresh whole blood=plasma＞banked blood＞normal saline=lactated Ringer's=gelofusin=Haemaccel=hydroxyethyl starch＞mannitol. The solubilities of the anaestheties in all priming fluids increased logarithmically at lower temperatures (p＜0.05). The volume-fraction estimates of the partition coefficients were within approximately ±20% of the measured values for all values of solubility. The corresponding estimates of solubility for CPB blood sampies were between-36% and +24% of the measured values. During normothermic CPB, blood solubility of volatile anaesthetics would be unchanged when using plasma, slightly reduced when using banked blood and markedly reduced when using crystalloids and coiloids.