This report gives an overview of knowledge in Sweden pertaining to the nuclear weapons threat in the context of civil defence, and has been compiled on behalf of the Swedish Civil Contingencies Agency (MSB). The purpose is to identify the most important knowledge gaps at present, and indicate prioritized areas for future research. In summary the main conclusions are that, although extensive research has been performed in the past, it is unclear to what extent this knowledge is known and actively used among relevant actors today. Furthermore, in order to direct future research in this area to relevant topics, the aims of civil defence must be further specified.