A number of 'roadmapping' activities are being carried out internationally with the aim of planning and facilitating transitions to hydrogen energy systems. However, there is an evident discrepancy between the treatment of quantitative and qualitative information in the majority of roadmapping efforts. Whilst quantitative information is frequently analysed in numerical and computational models, conversely qualitative information tends to be incorporated on a significantly more ad hoc basis. Previous attempts at incorporating qualitative considerations have not usually been systematised. In this paper we present a methodology aimed at increasing the rigour with which qualitative information is treated in hydrogen roadmapping activities. The key changes and actor mapping (KCAM) methodology was developed as the primary qualitative component of the European Hydrogen Energy Roadmap project 'HyWays'. KCAM, developed from a well known general systems development model, constitutes a means of qualitatively analysing variable hydrogen supply chains that is structured, systematic and flexible. (c) 2006 International Association for Hydrogen Energy. Published by Elsevier Ltd. All rights reserved.