The competitive adsorption of sodium p-octylbenzenesulfonate (SOBS) and benzyl alcohol (BzOH) onto solid α-alumina at 35°C with and without 0.1 M NaCl has been studied using high-performance liquid chromatography (HPLC). Calculations of the individual area requirements of SOBS and BzOH in the adsorbed film were undertaken at the saturation level (plateau) of the SOBS adsorption isotherm. The lamellar liquid crystalline D phase of the system SOBS/BzOH/water was investigated by means of x-ray measurements in order to determine the area requirements. The discrepancies found between the area requirements in the D phase and on the α-Al2O3 reveal that the electrostatical headgroup repulsion will, on the solid surface, prevent the SOBS molecules to pack as in the D phase.