AbstractLow energy electron diffraction is a surface sensitive tool which is most widely used for the determination of surface symmetries and equilibrium atomic positions. Experimental and theoretical advances made in the past five years make it possible now to use LEED also for the characterization of a wide variety of surface defect structures. In this paper a variety of experimental results involving analysis of diffracted electron beam shapes as a function of primary electron beam energy, adsorbate coverage, crystal tem-perature and ordering time are presented. These experimental results coupled with kinematic theory, allow the determination of step density, size and shape of reconstruction domains and overlayer islands, island size distribution in an overlayer during growth, and the mode of growth.