The equilibrium vapor pressures over GdCl3, GdBr3, alpha-GdI3, TbCl3, TbBr3, and alpha-TbI3 were measured by the torsion-effusion method. The obtained data are well represented in the covered temperature ranges by the following selected equations: [GRAPHICS] Considering the vapor consists only of the monomeric form, by the second- and third-law treatment of the experimental data, the following standard sublimation enthalpies of the compounds were derived: Delta(sub)Hdegrees(298 K) = (311 +/- 4, 292 +/- 2, 279 +/- 2, 296 +/- 4, 288 +/- 4, and 279 +/- 2) kJ.mol(-1) for GdCl3, GdBr3, alpha-GdI3, TbCl3, TbBr3, and alpha-TbI3, respectively.