Surface enhanced Raman scattering (SERS) and differential capacitance have been used to study interfacial structure in LiBr-containing dimethylsulfoxide (DMSO) at Ag electrodes. The potential-dependent orientation of this solvent is driven by interactions of the O atoms with the AE surface at positive potentials and by interactions of the S atoms with the surface at negative potentials. Significant spectral changes are observed at potentials in the vicinity of the pzc indicating reorientation of interfacial solvent molecules. Evidence for unique potential-dependent interactions of Li+ and Br- with DMSO and trace amounts of H2O in the electrochemical interface have been uncovered on the basis of their spectral signatures. Potential-dependent molecular pictures of the interface in this system are proposed.