The order parameters of lipophilic chains in the liquid crystalline phases of the C12E3/decane/water ternary system have been studied by deuterium NMR spectroscopy. The order parameters derived indicate that the decane molecules added to the C12E3/water system penetrate into the lipophilic alkyl layer of the surfactant and make the structure of the lipophilic layer disordered. The lipophilic layers in the reversed hexagonal phase are more disordered than those in the lamellar phase.