Different techniques (light transmittance, optical microscopy, X-ray diffraction, small-angle X-ray scattering, viscosity, and electric conductivity) were used to characterize the structure of the sponge (L-3) phase in the bulk of the partial isothermal surface of the phase diagram of the sodium dodecyl sulfate (SDS)/1-pentanol (C-5)/cyclohexane (C-6)/water mixture, with [SDS]/[C-5] = 0.17 (square brackets represent the percent molar concentration). The results accumulated from the different experimental techniques point toward an inverted structure for the L-3 in the concentration range investigated. A water layer of thickness delta separates two nonconnected regions in C-6. This water layer is separated from C-6 by the polar heads of the SDS and OH groups from the C-5 molecules.