  Polarimetry provides key physical information on the properties of
interacting binary systems, sometimes difficult to obtain by any other type of
observation. Indeed, radiation processes such as scattering by free electrons
in the hot plasma above accretion discs, cyclotron emission by mildly
relativistic electrons in the accretion shocks on the surface of highly
magnetic white dwarfs and the optically thin synchrotron emission from jets can
be observed. In this review, I will illustrate how optical/near-infrared
polarimetry allows one to estimate magnetic field strengths and map the
accretion zones in magnetic Cataclysmic Variables as well as determine the
location and nature of jets and ejection events in X-ray binaries.
