  We study weak localization in chains of metallic rings. We show than
nonlocality of quantum transport can drastically affect the behaviour of the
harmonics of magnetoconductance oscillations. Two different geometries are
considered: the case of rings separated by long wires compared to the phase
coherence length and the case of contacted rings. In a second part we discuss
the role of decoherence due to electron-electron interaction in these two
geometries.
