Organised cervical screening programmes are a combination of arrangements designed to maximise benefit and minimise harm associated with cervical cancer at the population level. Many organised programmes are described as 'evidence-based', reflecting an expectation that healthcare should be based on the tenets of Evidence-Based Medicine (EBM). EBM is both normalised and contested. As part of a larger study of how cervical screening came to be the way it is, we conducted a grounded theory study of cervical screening experts' perspectives on evidence and its use in guideline development processes. We sampled from several countries and across a range of professional backgrounds. Analysis was developed through transcript coding and memo writing, using constant comparison to develop insight and connections between concepts. We found that the 'evidence-based' descriptor was used rhetorically to indicate scientific trustworthiness; in short 'evidence-based' indicated 'good'. Experts held ideal conceptions of evidence and its use as objective and value-free, yet reported experiences that suggested those ideals were unattainable in practice. The 'evidence-based' ideal included restricting what counts as evidence to matters of science and epidemiology. This produced pronounced attention to matters of efficacy and effectiveness of cervical screening tests, and neglected decisions relating to the other arrangements that combine to produce an organised screening programme. Rhetorical use of the 'evidence-based brand' appeals to a particular kind of authority: one which is difficult to achieve in practice, and belies the variety of information that is required and the socially negotiated nature of policy and programme decisions.