Radio waves must necessarily travel through the lower atmosphere for any ground or space link where at least one end is near the ground. Consequently, the influence of the lower atmosphere on wave propagation act on the whole radio spectrum and the influence becomes much greater above 30 MHz. Optical propagation is also affected by the lower atmosphere. Though all the possible physical phenomena which can influence wave propagation are clearly identified, difficulties occur when predicting the effects of these phenomena, mainly due to insufficient knowledge of radio and optical meteorological parameters. Therefore, the objectives of this symposium were: (a) To discuss the present knowledge of the meteorological and radiometeorological parameters which may have an influence on terrestrial or earth-space radio links, (b) To discuss the various models and the various methods of predicting the effects of these parameters on radio wave propagation, (c) To discuss the effects of turbulence and particle scattering on optical propagation, and (d) To investigate possible methods to overcome the perturbations due to these propagation effects. (Author).