An arbitrary number of dislocations were freshly introduced in wurtzite ZnO bulk single crystals by plastic deformation at high temperatures (923-1123 K), and the optical properties were examined by photoluminescence spectroscopy. ZnO, including a high density (more than 10(9) cm(-2)) of dislocations, showed excitonic light emission with photon energies of 3.100 and 3.345 eV, as well as their LO-phonon replicas, at a temperature of 11 K, and the intensities increased with increasing dislocation density. (c) 2008 American Institute of Physics.