This chapter has described the application of computer simulations to the study of crystal surfaces. The methods are general and can be applied to surfaces of any structure. Straightforward extensions of the techniques enable many two-dimensional defects and interfaces to be studied, including stacking faults, grain boundaries, shear planes and interfaces between different materials. Clearly, more work is required in applying these methods to the defective surface and solid gas or solid-liquid interfaces. The problem of transferability of potentials to the surface, particularly in the less ionic materials needs more study. If suitable potentials can be derived for the more covalent materials, lattice simulation techniques could provide a valuable method for studying the more complex oxide and semiconductor surfaces.