Two elpasolite crystals Cs2NaYBr6 and Cs2NaYCl6, both doped with U3+ were investigated. The emission from the (4)G(7/2), F-4(3/2), and I-4(11/2) levels was found. Decay times of the visible emission were measured as a function of temperature. The strong influence of temperature on the decay times is discussed in terms of strong phonon coupling of the 5f(3) and the 5f(2)6d(1) bands. Upon IR excitation a red emission, assigned to the 4G(7/2) --> I-4(9/2) transition, was observed only in the bromide. The anti-Stokes emission is due to step by step absorption. The observed dependence of these phenomena on environment is discussed briefly.