In line with contemporary political and sociological research on science and regulation, this article problematizes the notion of ‘scientific evidence’ as something independent from and prior to political values. The production of scientific or technical criteria supporting regulatory politics is referred to as ‘regulatory science’ in the fields of policy studies and the sociology of science and technology. Evidence-bases are an example of regulatory science and they illustrate the latter’s intimate relation with political values. I will briefly outline how evidence-bases are not a neutral basis for politics, but that they are constructed through politics and interested groups. Taking the European health claims debate as an example, I show that there exists no unitary notion of evidence, but a confrontation of two scientific frameworks, supported by different expert networks, and proposing different conceptions of what scientific 'evidence' is. In regulatory matters, scientific evidence alone cannot settle disputes once and for all because the evidence is precisely what's at stake.