Within recent years, a new satellite technique has been successfully developed for studying the oceans: altimetry. The SEASAT experiment presents a particular interest because of the great accuracy of the altimeter data, though its capabilities are bounded by the accuracy of the trajectory resistitution. The altimetric signal variations result from both marine and tectonic effects, the discrimination of which may be difficult. In the present study on the western Mediterranean Sea, the altimeter data processing, the satellite trajectory, and the geoid features are considered. The satellite topography of the Mediterranean Sea surface shows irregularities which are 1 order of magnitude greater than the expected oceanic effects and so are mainly connected to the earth structure. In fact, in spite of neglecting the oceanic effects, correlation with emerged land (islands) or immerged land (bathymetry) and also with main tectonic features can be seen. In particular, evidence exists for isostatic compensation of Airy type in the continental margins and oceanic areas.