We discuss the observational evidence for propagating electron distributions in the solar corona as obtained from type III observations. The location of the beam acceleration region together with the effects of the ambient medium on beam propagation are discussed in the framework of recent observational and theoretical developments. The results of combined X-ray and radio observations obtained during and after the Solar Maximum Year are summarized. Special attention is paid to the effect of the small-scale structure of the corona on the observed radio emission. We outline various desirable developments which are necessary to improve the understanding of the behaviour of charged particle beams in magnetized plasmas.