Abstract Vibronic transition probabilities Avibin the emission spectra of Gd3+ in LaF3, LiYF4 LaAlO3, and La2O3 are reported. Data for Cs2NaGdCl6 and YOCl, obtained from the literature, are also discussed. The vibronic transition probabilities vary by two orders of magnitude: from Avib = 2 s−1 to Avib = 114 s−1 for the 6 P 7 2 → 8 S 7 2 transition of Gd3+ in LaF3 and YOCl, respectively. The difference is mainly due to differences in the polarizability of the ligands of Gd3+. The Stokes vibronic transition probability in the 6 P 7 2 → 8 S 7 2 transition in LaAlO3:Gd3+ and the anti-Stokes vibronic transition probability in 6 P 7 2 → 8 S 7 2 transition in LiYF4:Gd3+ are measured as a function of temperature. The temperature dependence is in agreement with existing theories.