In recent years, there has been great interest in scenario-based design and other forms of user-centred design. However, there are many design processes that, often for good reason, remain technology-centred. We present a case study of introducing scenarios into two digital library development processes. This was found to disrupt established patterns of working and to bring together conflicting value systems. In particular, the human factors approach of identifying users and anticipating what they are likely to do with a system (and what problems they might encounter) did not sit well with a development culture in which the rapid generation and informal evaluation of possible solutions (that are technically feasible and compatible with stable system components) is the norm. We found that developers tended to think in terms of two kinds of user: one who was exploring the system with no particular goal in mind and one who knew as much as the developer; scenarios typically work with rich...