A combined C-D stretching Raman and deuterium NMR spectroscopic method was applied to a study of the molecular and phase structure of the C12E5-water system, where C12E5 denotes a nonionic surfactant CH3(CH2)(11)(OCH2CH2)(5)OH. Spectroscopic measurements were performed on aqueous solutions of six selectively alkyl-monodeuterated species, an oxyethylene-partially deuterated species, an alkyl-block-deuterated species, and an oxyethylene-block-deuterated species. The ranges of the compositions and temperatures studied were 40-75 Wt % C12E5 and 0-80 degreesC, where a number of anisotropic and isotropic phases are observed. The Raman results showed that the trans fractions of the C-C bonds of the dodecyl chain decrease continuously with increasing temperature across different phases. The NMR results showed, on the other hand, that, with increasing temperature, the order parameters exhibit distinct discontinuities at the phase transition from the normal hexagonal phase to the lamellar phase. The results from the two spectroscopic methods reflect the difference in their time scale. The behavior of the order parameters was explained by taking account of two factors, the chain order and the conformational order. The observed discontinuities of the order parameters at the phase transition can be ascribed to the change of the chain order, which is caused by wobbling motions of the whole surfactant molecule. The temperature-dependent shift of the position on the alkyl chain, at which the order parameters show their maximum, is explained by the different rates of reduction, with increasing temperature, of van der Waals forces between the alkyl chains and hydrogen-bonding forces between the oligo(oxyethylene) chain and water. The stability of the lamellar phase is maintained by the presence of interlamellar water.