Abstract19F NMR spectra and relaxation times T,1, T2, T1e and electric conductivity in isostructural polycrystalline pentafluoroantimonates (III) M2SbF5 (M = Rb, K, Cs, Tl, NH4) are measured. It is found that the observed changes in the NMR spectra and relaxation times with temperature are determined by three types of motion: anisotropic and isotropic reorientations of [SbF5E]2− octahedra and diffusion motion of the fluorine ions. Parameters of these motions are found. All the compounds investigated show high conductivity at high temperature, amounting in the case of thallium and ammonium salts the values of σ = 101 to 100Ω−1 m−1 typical of superionic crystals. It is shown that the observed high conductivity is determined by fast diffusion motion of fluorine ions. On the basis of the data obtained a mechanism of fluorine ion diffusion is proposed. In (NH4)2SbF5 at 398 K a phase transition is found.