The extensive use of low-energy accelerators in non-nuclear physics has now reached the stage where these activities are recognized as a natural field of investigation. Many other areas in physics and chemistry have undergone similarly spectacular development: beam foil spectroscopy in atomic physics, studies in atomic collisions, materials implantation, defects creation, nuclear microanalysis, and so on. Now, this most recent activity by itself and in its evident connec tion with the others has brought a new impetus to both the funda mental and the applied aspects of materials science. A summer school on "Material Characterization Using Ion Beams" has resulted from these developments and the realization that the use of ion beams is not restricted to accelerators but covers a wide energy range in the developing technology. The idea of the ion beam as a common denominator of many act1v1t1es dealing with surface and near-surface characterization was enthu siastically received by many scientists and a school on this subject received the positive endorsement of NATO. The Advanced Study Institute on Materials Science has assumed for us the status of an "institution" leading to better contact among the many laboratories engaged in this field. The fourth Institute in this series was held in Aleria, Corsica, between August 22 and September 12, 1976.