An important direction in recent thinking about public understanding of science and technology is embodied in the international trend within many democratic countries towards the promotion of citizen engagement. These developments entail the participation and deliberative involvement by lay publics in planning, decision-making and policy-making situations. In this paper we argue that citizen engagement exercises can usefully be understood as information systems. This characterization leads us to propose that the effectiveness by which such exercises utilize sources of knowledge—what we term their translation quality—should be adopted as a new criterion for their evaluation. We illustrate the applicability of this proposal by analyzing the GM Nation? public debate, a government-sponsored citizen engagement exercise that took place in Britain in 2002—3.