The UK controversy over the health risks of mobile phones was at its peak around 1999-2000, at a time when policymakers were beginning to endorse moves towards greater openness in the practice of expert advice. One explanation for the subsequent calming of this controversy is that people's sense of the benefits outweighed the minor uncertainties. However, this fails to explain the politics of mobile phone technology and, by positioning expert advice as neutral, offers no lessons for future expert practice. In this article, I argue that the mobile phones case can more productively be seen as one of public experiment. Rather than seeking closure, experts opened up the issue, made explicit previously obscured uncertainties and invited new research questions. In doing so, they remobilised previously static constructions of both science and public concern. This analysis challenges the distinction between science-as-expertise and science-as-experiment, with important implications for advisory practices and structures. This article is published as part of a thematic collection dedicated to scientific advice to governments.