Display omitted •X-ray scattering experiments were performed on DMPC with and without halothane.•Molecular dynamics simulations were performed on similar systems.•Halothane causes an increase in DMPC chain spacing.•Pressure causes a reduction in DMPC chain spacing. Using a combination of high pressure wide angle X-ray scattering experiments and molecular dynamics simulations, we probe the effect of the archetypal general anaesthetic halothane on the lipid hydrocarbon chain packing and ordering in model bilayers and the variation in these parameters with pressure. Incorporation of halothane into the membrane causes an expansion of the lipid hydrocarbon chain packing at all pressures. The effect of halothane incorporation on the hydrocarbon chain order parameter is significantly reduced at elevated pressure.