We present a review of the current state of atomistic theory and computer s
imulation methods in the study of grain boundary structure and diffusion pr
operties. We review the multiplicity of possible local minimum energy struc
tures that arise for the structure of the same grain boundary, particularly
in the case of a grain boundary in an ordered alloy. We also review recent
structural studies performed for randomly generated grain boundaries. The
basic features of the interaction of vacancies with the grain boundary are
reviewed for the case of special boundaries. We describe the use of a combi
nation of molecular statics/Monte Carlo techniques for the calculation of d
iffusion properties along grain boundaries based on many-body interatomic p
otentials. The method is exemplified in the results obtained for a special
grain boundary in the intermetallic compound NiAl. Finally, we describe the
studies that have been carried out using molecular dynamics for special gr
ain boundaries in fee metals, showing that both vacancy and interstitial me
chanisms may be important. The advantages and disadvantages of these techni
ques for the study of grain boundary diffusion are discussed.