The world’s only satellite organization providing mobile communications on a commercial basis is the International Maritime Satellite Organization (Inmarsat). This paper reviews the origins of the organization and the needs of the shipping and offshore industry that led to its formation. The current system and its operations are described. The success achieved so far by Inmarsat in providing the satellite capacity for telephone, telex, facsimile and data communications to the maritime community makes it apparent that the system could also be used to provide capacity to the aeronautical community. Also, studies are now being made on future configurations of the system in which it may be possible to integrate a polar-orbiting satellite system, such as Sarsat-Cospas. Inmarsat is proceeding with the procurement of a new series of satellites that would come into operation from 1988. This paper reviews the enhanced capabilities that these new satellites will provide in the context of the requirements for mobile communications via satellite in the next decade.