The Viking lander-to-orbiter relay links make it possible to perform measurements of the electrical properties of the Martian surface by the bistatic technique. The electromagnetic signals radiated by the lander antenna at 381 MHz, in fact, reach the orbiter both directly and after reflection from the Martian terrain as the orbiter rises and sets with respect to the lander. The fading pattern of the signal intensity received at the orbiter therefore contains information on the refelction coefficient of the terrain and hence on the relative dielectric constant &egr;r and the conductivity &sgr; in the vicinity of the lander. The signal amplitude's fading patterns collected with the Lander 1 to Orbiter 1 relay link were of good quality and led to the determination of &egr;r=3.3¿0.7 in the vicinity of Lander 1 (when the quasi-specular theory was used and &sgr; was assumed to be between 10-3 and 10-5 mho/m). These electrical properties are similar to those of pumice and tuff. The dielectric constant of the surface near the Lander 2 site is estimated to be &egr;r=2.8--12.5.