Optically stimulated luminescence (OSL) was excited at LNT by monochromatic light in x-irradiated natural quartz crystals. Excitation maxima appeared at 290 and 310 nm. The phototransferred thermoluminescence (PTTL) of these crystals showed excitation maxima at the same wavelengths, indicating that carriers are optically stimulated from the same traps. This is supported by the finding that the same wavelengths are most efficient for optical bleaching caused by prolonged illumination. The effects of thermal annealing to gradually increasing temperatures on the OSL were investigated and a correlation to thermoluminescence (TL) peaks was found. The OSL intensities showed sharp decreases after annealing to 160, 190 and 280 K; these temperatures coincide with the temperatures of the main TL glow peaks. It appears therefore that the OSL and the main TL peaks between liquid nitrogen temperature (LNT) and room temperature (RT) are due to the same donor levels. The emission spectrum of the OSL showed that this emission is composed of some bands, which appear also in PTTL as well as in x- and photoluminescence, indicating that the same luminescence centres are responsible for these emissions.