The emission spectrum of LaF{sub 3}:Gd shows an anti-Stokes vibronic line coupled to the {sup 6}P{sub 7/2} {yields} {sup 8}S transition. Recently we have shown that X-ray excitation of Gd{sup 3+}-containing compositions can yield very efficient Gd{sup 3+} emission (4, 5). In this way it is possible to study vibronic transitions in the Gd{sup 3+} emission spectra. The fact that the ground state ({sup 8}S) of the Gd{sup 3+} ion is not split makes it easy to observe and interpret these spectra. In view of our results with Stokes vibronics on the {sup 6}P{sub 7/2} {yields} {sup 8}S electronic transition of the Gd{sup 3+} ion, we tried to observe also the anti-Stokes emission.