The dislocation structure in olivine crystals has been studied by means of X‐ray topography. The dislocations have Burgers vector [100] or [001], the majority of the dislocations lying in the (100) or the (001) plane and being of the edge, screw or mixed type. Some dislocation tangles are apparently closely connected to Ca‐rich inclusions. The observed dislocation structure and its possible origins are discussed in relation to previous electron diffraction studies and slip line observations on olivine crystals deformed naturally or experimentally at various temperatu