Mechanical anisotropy of compression-moulded polymer blends of poly(styrene-block-butadiene-block-styrene) triblock copolymer (KR05) with methyl methacrylate-styrene copolymer (MS-200) was examined and correlated to microstructure of the blends. The KR05 phase of the blends exhibits lamellar morphology and phase separation from the MS-200 phase. For compression mouldings of the KR05-enriched blends in which most of MS-200 inclusions are relaxed to isotropic spheres the mechanical anisotropy is clearly discernible, consequent on anisotropy of the lamellar arrangement of the KR05 matrix. When KR05 lamellar morphology of the KR05-enriched blends is viewed on scales over the MS-200 domain size, stereoscopic anisotropy of the lamellar orientation is perceived with some disarrayed lamellae in places. Such anisotropy would be prevalent in the mouldings as in compression-moulded KR05, and could occur in somewhat changeable directions of heat transfer on cooling the melt during compression moulding. The mouldings show enhanced toughness when the impact stress is imposed on the mouldings in the direction along which the deformation of the orderly KR05 lamellae may predominate in the whole change of the lamellar morphology on impact.