I have been entrusted with the task of describing the work of URSI since its first General Assembly in 1922 up to the present time. It will be appreciated that, given the multiplicity and the very rapid developments of subjects, it seems almost impossible to cover all the aspects of radio science and to do justice to the ingenuity and skill of all those who, over the years, contributed to the growth and reputation of our Union. However, I shall try to refer to the most striking features of the scientific life of URSI, leaving aside the administrative aspects as far as possible. To apprehend the incredibly fast advances achieved over the past 75 years in our domain of investigations, it seems worthwhile referring in some detail to the programme of the first two General Assemblies. As stated by J.H. DELLINGER in 1963 : «The history of our Union is one of steady growth and of effort to coordinate the international scientific foundations of the fantastically extending roles of radio and electronic applications. Our domain extends over the Earth, throughout the solar system, and out among the galaxies. We can be sure of one thing : when man reaches the outermost limits of the observable Universe, he will materially be assisted by means of radio for communications navigation and control using the electromagnetic waves envisaged by the genius of Maxwell a hundred years ago?