The application of hydrophilic penetration enhancers enables an increased bioavailability of dermally and transdermally applied drugs. However, until now, the respective mode of action on a molecular scale is not fully understood. Within this thesis, several investigations were made to gain information about the interaction of specific hydrophilic penetration enhancers with stratum corneum lipids. In detail, the influence of the hydrophilic penetration enhancers water, urea, taurine, dimethyl sulfoxide, glycerol, propylene glycol, 1,2- and 1,5-pentandiol on the different stratum corneum lipid models of multilayer, oligolayer, solid supported single bilayer and liposomes has been investigated using infrared spectroscopy, neutron reflectivity, fluorescence spectroscopy and photon correlation spectroscopy. The results of this thesis provide detailed and innovative information about the mode of action of the used enhancers.