Thermoluminescence (TL), optical absorption, and electron paramagnetic resonance (EPR) have been used to characterize point defects in Mg-doped stoichiometric LiNbO3. A broad TL emission, peaking at 440 nm, is observed near 94 K when these crystals are irradiated at 77 K and then rapidly warmed. X rays and below-band-gap lasers (325 and 355 nm) are equally effective in producing the TL peak. During excitation, holes are trapped on oxygen ions adjacent to lithium vacancies and electrons are trapped on niobium ions at regular lattice sites. These defects both have characteristic EPR spectra, and the trapped electron center has an optical absorption band peaking at 1200 nm. Upon warming, the electrons become thermally unstable near 94 K and migrate to the trapped-hole sites where radiative recombination occurs. We suggest that the near-edge charge-transfer absorption band from Fe3+ impurities, nominally present, provides the mechanism by which below-band-gap light initially produces the separately trapped holes and electrons. © 2002 American Institute of Physics.