This volume contains most of the invited and contributed papers presented at the second international conference devoted to the general topic "Vibrations at Surfaces" and which took place from 10 to 12 September 1980 at the Facu1tes Notre-Dame de 1a Paix in Namur, Belgium. The conference was organized to review the large amount of information gathered in this field over the late seventies as a result of th~ rapid improvements and dissemination of surface spectroscopic technique such a electron energy loss, infrared and Raman surface spectroscopies. Much time was devoted to Raman spectroscopy of adsorbed mo1e­ 'cu1es. After several years of vivid debate over the causes of the observed large enhancement of Raman cross section, a clearer pic­ ture emerges from the papers presented here: the actual value of the enhancement factor does depend in a complicated manner on long range surface roughness, atomic-scale roughness and the dielectric properties of the substrate as well as on the electronic structure of the molecule in its adsorbed state. Less controversial are the results obtained with electron energy loss spectroscopy (EELS) and several sessions of the con­ ference were devoted to the approach. As witnessed by the growing number of laboratories using the technique, EELS is now a mature spectroscopic tool for the characterization and analysis of the chemisorption bond.