The contribution from vacancies to the expansion of graphite lattice along theCaxis and to its contraction along theaaxis has been calculated on the basis of the dependence of the spacings between the carbon atoms on the bond order. It is found that αvc= 1.32, αva= −0.46. Using the same model the effect of interstitials contained in various complexes on the graphite expansion along theCaxis has been estimated. The relationships obtained have been used for the analysis of experimental data on the change in theCandaparameters of graphite irradiated under various conditions. Comparison with other models is also made.