Abstract
Scattering of waves and particles from N discs fixed in a plane is studied. Various boundary conditions on the scatterers, corresponding to mesoscopic quantum physics, acoustics or electromagnetism, are considered. An exact formalism allowing us to calculate the S-matrix, its scattering resonances and far-field form functions is developed for systems with discrete 
, 
and 
symmetries. It extends the Korringa-Kohn-Rostoker method developed in the context of solid state physics and generalizes the works of Berry and of Gaspard and Rice in quantum chaos.