Among the various methods of additional heating of toroidal magnetically confined plasmas by high frequency fields, heating near the lower hybrid frequency appears promising. With principal reference to the results of the WEGA-Tokamak, complemented by results on analogous experiments, the discussion centers on three points : first, the coupling of the H. F. energy to the plasma ; secondly, the modifications induced in the plasma parameters and finally ion heating by absorption of the H. F. energy