Adsorbed to a rigid substrate, dimyristoylphosphatidylcholine multibilayers attain full hydration in all mesophases.

Whether hydrated from vapor or immersed in liquid water, aligned multibilayers of dimyristoylphosphatidylcholine adsorbed to a single mica "substrate" are shown by neutron diffraction to hydrate in all mesophases (e.g., Lbeta', Pbeta', and Lalpha) to the same extent as their liposomal counterparts suspended in liquid water. These data clearly demonstrate that the commonly accepted vapor pressure paradox does not exist.