Energy, and especially its minimization, are factors which govern all physical processes. Given sufficient time and thermal activation, for instance, grain boundaries will move so as to tend towards a regular array of 14-sided grains. When a grain boundary intercepts a surface, the energies of the surface and boundary govern the precise form of the triple-point. Regions of mismatch within the solid, especially those associated with dislocations, interfere with dislocation cross-slip and thereby affect mechanical properties. The present volume comprises a compilation of measured values of the energies of various planar defects in solids: including grain boundaries, stacking-faults, twins, etc. for a wide range of material groups: metals, semiconductors, oxides, carbides, diamond, graphite, nitrides, halides, ice, and various minerals. The 451 entries cover the period from 1958 to 2014.