Electron paramagnetic resonance (EPR) for specially doped LiNbO3 crystals was determined. Study of the charge transfer and the photosensitivity in these crystals determined the ions, which participate on the charge transfer processes. In doubly doped crystals with Fe:Cr and Fe:Ce the decay of the EPR signal was less than the decay time in LiNbO3:Fe:Mn. some inherited impurities in these crystals like Mn and Fe were detected. The effect of the inherited impurities on the decay and growth of the EPR signal was estimated by comparing the results with homegrown LiNbO3 crystals.© (1997) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.