Two broad photoluminescence (PL) bands peaking near 502 and 725nm are observed at room temperature in Ag-doped Li 2 B 4 O 7 crystals pre-irradiated at room temperature with X-rays. Their respective excitation bands peak near 297 and 325nm. The requirement that the crystal be pre-irradiated establishes that these emissions are not related to Ag + ions. Electron paramagnetic resonance (EPR) helps assign models to the PL bands. EPR spectra show that two substitutional Ag 2+ trapped-hole centers and one interstitial Ag 0 trapped-electron center are produced at room temperature by the X-rays. A majority of the Ag 2+ ions have no neighboring defects (and are referred to as Center A) while the remaining Ag 2+ ions have a nearby defect (and are referred to as Center B). The PL bands are assigned to these two Ag 2+ ions (the 502nm emission to Center A and the 725nm emission to Center B). A charge-transfer mechanism is responsible for the observed luminescence, i.e., an electron from a neighboring oxygen ion, upon excitation, moves to the Ag 2+ ion and produces a Ag + ion with an adjacent O − ion. This excited-state complex quickly decays radiatively and the original Ag 2+ and O 2− ions are restored. Optical absorption related to Ag 2+ and Ag 0 defects are observed in the ultraviolet and visible after the Ag-doped crystals are X-ray irradiated at room temperature.