The dielectric functions of disordered Ag1−xInx alloys (x≤0.12) were obtained ellipsometrically in the 1.2–5.5-eV energy region. In the low-energy region, the intraband scattering rate, described by τ−1=τ−10+βω2, increases with increasing In concentration. The increasing positive values of β with increasing In content do not agree with a calculation based on the assumption of a spherical Fermi surface and isotropic scattering from an impurity represented by a screened Coulomb potential. The onset energy of the L3→L’2(EF) transition, 4.03 eV for pure Ag, shifts to higher energies, while that of theL’2(EF)→L1 transition, 3.87 eV for pure Ag, shifts to lower energies. This is only partly attributable to the rise of the Fermi level EF caused by an increase in the average number of electrons per atom due to the In solute and to the narrowing of the Ag 4d bands. The L1 band may also lower as In is added.