Spin-lattice relaxation rates and nmr linewidths of 7Li and 23Na have been measured up to 800 OC for Li2S, Li20, Na2S-and for Na20. Relaxation due to cation diffusion is observed with predominant dipole interactions in Li2S and LizO and quadrupole interactions in Na2S and Na20. Motional narrowing occurs below 300 OC. For Li2S, Li20 and Na2S cation jump frequencies in the regions of intrinsic and of extrinsic disorder are determined with apparent activation energies of about 1.4 and 0.7 eV for Li2S, 1.3 and 0.55 eV for Li20 and 1.3 and 0.7 eV for Na2S. Ionic conductivities calculated from the nmr data agree with conductivities determined directly within a factor 3