U3+:CaF2 single crystals with different dopant concentrations were grown in the presence or absence of PbF2 as oxygen scavenger by TGT. Multiple centers, at least including (U-ca(3+) - O-F(2-)) and (U-ca(3+) - F-i(-)), were investigated by absorption spectra measured in the wavelength range of 190-2500 nm. Absorption coefficient ratios in different samples indicates that the concentration of (U-ca(3+) -O-F(2-)) centers in U3+:CaF2 crystal grown with PbF2 was relatively low and almost remained constant. Without PbF2 as oxygen scavenger, (U-ca(3+) - O-F(2-)) centers with higher concentration are distinctly present in U3+:CaF2 crystal. The oscillator strength of the transition I-4(9/2) --> I-4(15/2) of (U-ca(3+) - F-i(-)), corresponding to absorption band at 896 nm, is larger than that of (U-ca(3+) - O-F(2-)). Color centers in U3+:CaF2 were studied by gamma-irradiation and heat treating in oxygen atmosphere. (C) 2004 Elsevier B.V. All rights reserved.