The monograph is devoted to a new branch of remote sounding of the iono­ sphere - ionospheric tomography. Adoption of tomographic methods seems to be an inevitable stage of the evolution of almost all diagnostic systems. Ad­ vanced techniques for remote sensing and progressive means for data process­ ing open the possibility of reconstructing the spatial structure of the medium on the base of tomography. In this book, mainly the problems of satellite radio tomography of the ionosphere are discussed, and only one subsection is alloted to optical ionospheric tomography. Modern radio sounding techniques make it possible by means of satellite facilities to probe the ionosphere within a wide range of varying positions of transmitting-receiving systems and to apply tomographic methods. In this connection, in recent years, active tomo­ graphic investigations of the ionosphere have been done. The purpose of this monograph is to set forth the tomographic methods developed for recovering the 2-D and 3-D structure of the ionosphere and to discuss experimental implementation of these methods. The topic of discus­ sion is reconstruction of electron density distribution and effective collision frequency. The structure of the ionosphere is known to be quite complex; along with a quasi-stratified background with large scale variations in elec­ tron density, there are also local irregularities of various scale sizes, including turbulent volumes.