The d-lipid bilayer with no ergosterol, composed of mainly monounsaturated C18:1 lipids, has a hydrophobic thickness of (32 ± 1) Å, 6 Å thicker than in the corresponding hydrogenous, more polyunsaturated membrane. The thickness is also somewhat higher than the one found in synthetic C18:1–C18:1 PC bilayers, as the deuterated lipid extract retains a fraction of the saturated C16:0 and C18:0 chains. The neutron scattering length density of the deuterated lipid chains,