The impurity and lattice contributions to the spin-lattice relaxation of Al-27 nuclei in nominally pure and lightly chromium-doped corundum (Al2O3) crystals are separated experimentally under the conditions of additional stationary resonance magnetic saturation of a pulsed NMR signal. The relaxation time T-i(lat) due to the lattice mechanism of the spin-phonon interaction is determined. (C) 1997 American Institute of Physics.