  We examine the effects of disorder in one-dimensional systems. We link the
case of a few impurities, typical of a short quantum wire, to that of a finite
density of scatterers more appropriate for a long wire or a macroscopic system.
Finally we investigate the effects of long-range interactions on the transport
in 1D systems. We predict in that case a conductivity behaving as $\sigma(T)
\sim T^2$.}
