Crystals of 7‐In2S3, a new modification of indium sulphide, grown by vapour transport, were studied by X‐ray topography (Lang technique) and electron microscopy. The most frequent defects are dislocations with Burgers vector of the typeb= [100]. Growth layers were also observed. Neither the dissociation of dislocations into partials nor any stacking faults could be detected. γ‐In2S3gradually decomposes in the electron microscope by loss of sulphur. This results in an agglomeration of point defects leading to stacking faults surrounded by dislocation loops with b parallel to