A correlation is observed between the ESR spectra (at 1.12 GHz) and the magnetization inversions of the spin glassAgMn for a Mn concentration of 8.3 at. %. This is because of rearrangement of the spin system during the magnetization inversions. The widths of the ESR linesW↑undW↓which correlate, respectively, with the reversals to positive and negative magnetization are different. This is ascribed to different values of the effective anisotropy constantKduring the two reversals. Thus a relationship is obtained between the ESR linewidth and the anisotropy constant.