Magnetic resonance absorption line shapes and widths in Li metal and CaF2 crystals have been measured as a function of radio-frequency power level. The measurements have been made on the Li7 resonance in Li at 77°K and 215°K and on the F19 resonance in CaF2 at room temperature. The measurements have been made from low rf power into the region of appreciable saturation, but not into the very high saturation region considered by Redfield. A decrease in δH, the peak-to-peak absorption derivative line width, was observed in both systems at sufficiently large values of H1, the rf magnetic field. The changes of line width in Li at various values of T1 and of characteristic motional frequency of the nuclei show good qualitative agreement with the criteria proposed in the recent theory of Tomita. Line-width data obtained by Redfield in aluminum are included for comparison. In the case of CaF2, where the spin-lattice relaxation proceeds via paramagnetic impurities, the decrease in δH occurs at appreciably higher saturation levels than is the case in Li and Al.