From July 1945 when the first nuclear test was carried out in the United States, up to the recent underground tests conducted by India and Pakistan in May 1998 (including the most powerful explosion ever - 58 megatons - in the USSR in 1961, 2419 nuclear tests, of which 543 were in the atmosphere, have been carried out by the United States, the USSR, the United Kingdom, France, China and the two Asian states already mentioned. In line with the Office’s usual practice, the two rapporteurs, Messrs Christian Bataille, deputy, and Henri Revol, senator, have carefully analysis the facts and circumstances based on a large number of interviews in metropolitan France, Polynesia and Australia. As far as France is concerned, they were able to make use of the earlier studies carried out by different foreign and French teams, and also the two basic appraisals done by the IAEA International Consultative Committee and the International Geomechanical Commission (1998), all of which suggested that Mururoa and Fangataufa were "the most carefully inspected areas on earth". Following the collapse of the USSR, and as a result of a United States policy of declassifying a large number of documents over the last decade, it has been possible to begin examining the organisation, procedures and results of nuclear tests, all of which was quite impossible at the end of the 1980s. All in all, for most of the nuclear test sites, this study provides unpublished data and analysis which should permit the different procedures and their consequences to be evaluated on the basis of properly verified facts and recent research, even though some of the consequences, notably as regards the two superpowers, are still far from allowing evaluation to any great extent.