The concern about bioterrorism has been apparent in the U.S. for several years. Thousands of letters containing powder and a message warning for anthrax have been documented. It was, however, not until in October-November 2002 that anthrax letters were sent. Five letters have caused disease in 22 persons and thousands have been exposed to the infectious agent. Five persons of the 11 with the rare lungform of anthrax have died. The contagious letters have also caused widespread contamination of the Congress Buildings and several postal buildings. In addition, post sorted at the same time as the anthrax-laden letters have been contaminated. Two of the fatal lung anthrax cases are supposed to have obtained the infection following exposure to such letters. The anthrax bacterium, Bacillus anthracis, has properties which make it attractive as a BW agents, and it has been developed as weapon in several states. It forms highly stable spores and the contents of the contagious letters have been described as spores of weapon grade. Former American weapon researchers have publically stated that the preparation of spores were very similar to the American preparation produced in the BW programme, which ended in 1969. The letters contained spores with an optimal size for aerosol dispersion and infection via the lungs. Moreover, the spores were in high concentration and very pure and they were assessed to have been treated in order to avoid clumpling. The perpetrator was not yet identified in June 2002. He is described by the Federal Police as a scientist who has worked with anthrax in a defence facility, i.e. he has the required knowledge and technical skill for producing anthrax spores of weapon-grade and he is protected to infection by vaccination.