The intercomparison of time and frequency standards is restricted by the inadequacy of terrestrial radio time transfer links in terms either of accuracy or of geographical coverage. The use of artificial satellites can improve this situation. (Blair, 1974; Chi and Byron, 1975; Markowitz et al., 1966; Ramasastry et al., 1973; Saburi et al., 1976; Steele et al., 1964; Yamamoto et al., 1976). Two experiments are described in which the geostationary telecommunications satellite Symphonie is used. A two-way simultaneous link is employed in order to eliminate the need to know the propagation delays. Details of a test carried out in December 1976 between Raisting (West Germany) and Pleumeur-Bodou (France) are given. Also, preliminary details of the time transfer experiment between Pleumeur-Bodou and Ottawa (Canada) are described.