(2SR,4RS)-7-Chloro-2-exo-[(E)-styryl]-2,3,4,5-tetra­hydro-1H-1,4-epoxy-1-benzazepine, C18H16ClNO, (I), crystallizes as a racemic twin in the space group P21 and the mol­ecules are linked into a chain of edge-fused R33(9) rings by a combination of C—H⋯O and C—H⋯N hydrogen bonds. The diastereo­isomer (2RS,4RS)-7-chloro-2-endo-[(E)-styryl]-2,3,4,5-tetra­hydro-1H-1,4-epoxy-1-benzazepine, (II), also crystallizes as a racemic twin, but in the space group P212121, and a two-centre C—H⋯N hydrogen bond and a three-centre C—H⋯(O,N) hydrogen bond combine to link the mol­ecules into a complex chain of rings. In (2R,4R)-7-fluoro-2-endo-[(E)-styryl]-2,3,4,5-tetra­hydro-1H-1,4-epoxy-1-benzazepine, C18H16FNO, (III), which is not isomorphous with (II), the mol­ecules are linked by a single C—H⋯O hydrogen bond into simple chains, but the mol­ecular arrangements in (II) and (III) are nonetheless very similar. The significance of this study lies in its observation of the variations in mol­ecular configuration and conformation, and in the variation in the supra­molecular aggregation, consequent upon modest changes in the peripheral substituents.