Lay and medical beliefs are not separate systems. The beliefs of somatizing patients, in particular, incorporate medical understanding and it has been argued that this increases the power that such patients exert in seeking treatment from doctors. To understand the nature and use of this power requires investigation of (i) how patients use medical ideas and language to explain their symptoms and (ii) how this process influences patients' expectations and evaluations of their doctors. We interviewed 68 patients, in whom no physical cause had been found for persistent physical symptoms. Their accounts of symptoms and of their experience of doctors were subjected to qualitative thematic analysis. As expected, patients used medical terms to explain their symptoms. However, these depicted explanatory themes which have long been familiar in traditional lay models: disease as a malign entity and imbalance between bodily forces. Patients' sense of authority over doctors derived, not from facility with medical language and ideas but from contrasting their own sensory, and therefore infallible, experience of symptoms with doctors' indirect and fallible knowledge. By providing explanations that questioned the reality of symptoms, doctors were perceived as incompetent and inexpert. Patients used their authority, not to seek treatment, but to secure naming of, and collaboration against, the disorder. Although these patients saw the doctors' role as limited and inexpert by comparison with their own, our analysis suggests ways in which doctors might more effectively engage with persistent somatizing patients.