Through the European controversy over agricultural biotechnology, genetically modified (GM) crops have been evaluated for an increasingly wide range of potential effects.  As the experimental phase has been extended into commercial practices, the terms for product approval have become more negotiable and contentious.  To analyse the regulatory conflicts, this paper links three theoretical perspectives: issue-framing, agri-environmental discourses, and technological development as a real-world experiment.Agri-biotechnological risks have been framed by contending discourses, which attribute moral meanings to the agricultural environment.  Agri-biotech proponents have emphasised eco-efficiency benefits, which can remedy past environmental damage, while critics have framed 'uncontrollable risks' in successively broader ways through ominous metaphors of environmental catastrophe.  Regulatory authorities have translated those metaphors into measurable biophysical effects.  They anticipate and design commercial use as a 'real-world experiment', by assigning greater moral-legal responsibility to agro-industrial operators who handle GM products.Expert-regulatory debate reflexively considers the social discipline necessary to prevent harm, now more broadly defined than before.  Official procedures undergo tensions between predicting, testing and prescribing operator behaviour.  In effect, GM crops have been kept continuously 'on trial'.