[en] Modern surface modification techniques, such as ion implantation, are capable of treating surface layers with properties very different from those of the bulk underlying material. By correlating measured chemical and structural changes, induced by a surface modification method, with the changes in the physical properties of interest, an understanding can be developed as to why a particular method of modification produces a surface layer with specific properties. There are a large number of modern analytical techniques capable of probing the chemical and structural properties of material surfaces. These methods are reviewed with emphasis on the techniques that are most commonly and commercially available. Examples of applications of these methods to surface-modified materials are given. 15 refs., 14 figs., 1 tab