Ultrafine Y2O3: Pr, Yb nanoparticles were produced by femtosecond pulsed laser ablation. Scanning and transmission electron microscope analyses indicated that these spherical particles have a diameter of about 10 nm with a narrow size distribution and no visible coalescence. These nanoparticles show much improved upconversion intensity compared to nanoparticles prepared by the sol-gel method and a new 510 nm emission band was observed. The time-resolved spectra indicated that the samples prepared by the laser method have longer decay time in spite of the smaller size, resulting from the exclusion of chemical residues, which lead to the enhancement of upconversion intensity. (C) 2010 Elsevier B.V. All rights reserved.