AbstractThe British government has established an Advisory Committee on Releases to the Environment (ACRE) to provide advice on the release of genetically modified organisms (GMOs). Regulatory participants regarded its remit, covering all ‘novel organisms’, as providing a scientific basis for the committee. ACRE's composition strengthens the role ofecologists and includes an implicit ‘public-interest’ representation, thus attempting to encompass diverse aims and views.The British government has invoked ‘sound science’ as the basis of its precautionary approach. In its manner of constituting ACRE, however, the government acknowledged the socially negotiated character of regulatory science. ACRE thereby embodies a tension between technical risk assessment and policy issues irreducible to scientific evidence.