[en] Despite the acknowledged significance of organisational culture in the nuclear field, previous cultural studies have concentrated on purely safety related matters, or been only descriptive in nature. New kinds of methods, taking into account the overall objectives of the organisation, were needed to assess culture and develop its working practices appropriately. VTT developed the Contextual Assessment of Organisational Culture (CAOC) methodology during the FINNUS programme. The methodology utilises two concepts, organisational culture and core task. The core task can be defined as the core demands and content of work that the organisation has to accomplish in order to be effective. The core task concept is used in assessing the central dimensions of the organisation's culture. Organisational culture is defined as a solution the company has generated in order to fulfil the perceived demands of its core task. The CAOC-methodology was applied in two case studies, in the Radiation and Nuclear Safety Authority of Finland and in the maintenance unit of Loviisa NPP. The aim of the studies was not only to assess the given culture, but also to give the personnel new concepts and new tools for reflecting on their organisation, their jobs and on appropriate working practices. The CAOC-methodology contributes to the design and redesign of work in complex sociotechnical systems. It strives to enhance organisations' capability to assess their current working practices and the meanings attached to them and compare these to the actual demands of their basic mission and so change unadaptive practices. (orig.)