  We review recent experimental progress on the saturation problem in metallic
quantum wires. In particular, we address the influence of magnetic impurities
on the electron phase coherence time. We also present new measurements of the
phase coherence time in ultra-clean gold and silver wires and analyse the
saturation of \tauphi in these samples, cognizant of the role of magnetic
scattering. For the cleanest samples, Kondo temperatures below 1 mK and
extremely-small magnetic-impurity concentration levels of less than 0.08 ppm
have to be assumed to attribute the observed saturation to the presence of
magnetic impurities.
