Why do governments engage in technology foresight? What lessons emerge from the results of national experiences in technology foresight? This special issue of the STI Review addresses these questions, and looks at the strengths and weaknesses of different methodologies, including Delphi surveys, and the reliability of their results. It also addresses the issues of industrial involvement, the scope for international collaboration in technology foresight and the potential consequences for international technology co-operation or competition. Studies of government foresight exercises and their results are presented for Australia, France, Germany, Japan, the Netherlands and the United Kingdom.