The effect of general anaesthetics is pressure-dependent. We have simulated a fully hydrated dimyristoylphosphatidylcholine bilayer with halothane (a general anaesthetic) embedded, at pressures of 1, 200 and 400 atm, respectively. We find that at higher pressures, halothane molecules tend to cluster together. Based on these results, we propose a possible mechanisms for pressure reversal of anaesthesia. (c) 2007 Elsevier B.V. All rights reserved.