At the beginning of the 20th century the collective imagination was fascinated and terrified by the discovery of radium. A scientific imagery sprang up around radioactivity and was disseminated by public lectures and newspaper articles discussing the ambiguous power of this strange substance. It was claimed that radium could be used to treat cholera, typhus and tuberculosis, but at the same time there were warnings that it could be used for military purposes. The media and the scientists themselves employed a rich vocabulary influenced by religion, alchemy and magic. The ambivalent power of radioactive elements exerted a great influence on science fiction novelists. This paper will examine some significant works published in Europe, America and Russia during the first decades of the 20th century and their role in the creation of the complex imagery of radioactivity that seized the public imagination long before the invention of the atomic bomb.