The mechanism of coarsening of coherent particles in solids is investigated via high-resolution electron microscopy (HREM). Ni based alloys are used for microscopic observation of interfaces between particles (gamma') and matrix (gamma). HREM images of neighboring particles are used to ascertain whether or not such particles have the same translation order domain (TOD), and to measure the distance between them. It is found that the distance between particles is influenced by the relationship between their respective TOD. Particles with different TOD show shorter separation distances.