The surface structure of α-TiCl₃, α-MgCl₂ and MgCl₂-supported catalysts was directly observed by high resolution transmission electron microscopy (HRTEM). Lattice fringes were clearly observed in the surface regions of the α-TiCl₃ and the α-MgCl₂. The surface structures of MgCl₂-supported catalysts shows that the MgCl₂ crystals were severely deformed by the processes of catalyst preparation. These results suggest that MgCl₂ crystalline region exhibits a correlation with the catalyst performance.