Various [001] twist-(001) boundaries in Cu with dispersed SiO2boundary particles have been observed with a transmission electron microscope. Boundary energies were determined with reference to the isotropic Cu-SiO2interfacial energy by measuring the misorientation-dependent shape of the boundary SiO2particles. When the boundary energy was plotted against misorientation, several energy cusps were clearly recognized at misorientation angles corresponding to low σ values; namely at Σ41A, Σ13A, Σ17A, Σ5 and possibly Σ29A.