High‐resolution electron microscopy technique has been applied to a detailed study of the 60° dislocations at the atomic layer molecular‐beam‐epitaxial GaAs/Si interface. Their deformation fields strongly interact with neighbor dislocations inducing irregular spacing between the cores and possible dissociations. Biatomic silicon steps were observed at the interface, but never inside 60° dislocation cores. Computer image simulation and elasticity calculations of the atomic displacement field have been used in order to determine the structure of the 60° dislocation; however, due to the Eshelby effect and to interaction with some neighbor dislocations, in many cases no theoreticalmodel could explain some observations.