Kerr activity is observed in pure Ag films in the vicinity of the plasma resonance (3.85 eV) when subjected to a strong external magnetic field. This inherent magneto-optical behaviour of Ag in a narrow wavelength range (0.12 eV) around the plasma resonance is explained utilizing the classical Lorentz-Drude model for the off-diagonal elements of the dielectric function. This activity is a consequence of a combined effect of the weakly damped free electron system and the sharp onset of d-band transitions. The possibility of enhancing the Kerr activity of amorphous TbFeCo alloys by Ag overlayers is also investigated. © 1988 Springer-Verlag.