An overview is given of the use of low energy ion scattering as a probe of surface structure with emphasis on work done using alkali ions. Various schemes for extracting structural information from the ion energy and angle distributions are discussed in terms of advantages and disadvantages of each. The scattering potential, which is the primary nonstructural parameter needed for analysis, is discussed in terms of recent experimental results. The structures of clean and reconstructed surfaces are discussed, with examples of measurements of layer relaxations on the Mo (111) surface and missing row reconstructions on the Au (110) and Pt (110) surfaces. Studies of adsorbate covered surfaces are presented with respect to location of the adsorbate and its effect on the structure of the underlying substrate. Finally, examples are given which demonstrate the sensitivity of ion scattering to surface defects and disordering on reconstructed Au (110) and Pt (110) surfaces and unreconstructed Mo (111) surfaces, and to ordering of adsorbates on Mo (001).