Ultraviolet light-irradiation induced spectral change was studied in cubic nanocrystalline Y2O3:Eu3+. Under the irradiation of the ultraviolet fights separated from xenon lamp, the excited charge transfer band of Eu3+ decreased after irradiation. The smaller the particle size and the shorter the wavelength, the larger the spectral change. It was attributed to the local structural change surrounding Eu3+ ions in/near the surface. Under the irradiation of the 266-nm pulsed laser, some Eu3+ in nanoparticles was reduced to Eu2+. (C) 2003 Published by Elsevier Science B.V.