Nuclear waste disposal in the USA is a difficult policy issue infused with science, technology, and politics. This issue provides an example of the co-production of scientific knowledge and politics through public policy. The proponents of a repository site at Yucca Mountain, Nevada, argue that their decision to go ahead with the site is based on ‘sound science’, but the science they use to uphold their decision is influenced by politics. In turn, the politics of site selection has been altered by the scientific knowledge produced.