IR, Raman and surface-enhanced Raman scattering (SERS) spectra of sulfanilic acid sodium salt (SANA) were recorded and analysed. The vibrational wavenumbers were computed by the density functional theory method using the B3LYP/6–31G* basis and found to be in good agreement with the experimental values. The effect of concentration and pH dependence on the SERS intensity of the molecule was also studied. The molecular plane assumes a tilted orientation with respect to the silver surface. The observed changes of the relative intensities of some enhanced bands and the presence of in-plane and out-of-plane modes of the phenyl ring suggest that the molecule assumes a more tilted orientation upon lowering the concentration of the adsorbate. Copyright © 2009 John Wiley & Sons, Ltd.