Owing to the tremendously rapid development of the sciences publi cations of congresses and meetings are frequently out-of-date by the time they appear in print. We endeavoured to publish the report of the Sym posium in Montreux in as short a time as possible. In order to reduce the cost, the manuscripts hat to be confined to few pages at the most and it was absolutely necessary to limit the number of illustrations. For the Symposium in question we invited all those authors of whom we knew they were acquainted with the medicinal application of fast elec trons to take part in a discussion...