BACKGROUND & AIMS Chronic pain has profound psycho-social consequences for the individual and those around them. Individuals encounter loss of function, poor emotional health and stigma. Associated with stigma is the experience of disbelief: when others do not accept the individual’s account of their pain as true. Whilst research alludes to the disbelief experience, there is a distinct lack of a coherent model that explains what happens. In this thesis I aimed to develop a tentative grounded-theory of disbelief. METHOD I utilised Strauss and Corbin’s (1998) approach to grounded-theory. Through a collaborating Pain Management department in the West Midlands, I recruited thirteen individuals experiencing chronic pain; nine were female and all were white British. Pain duration ranged from 3 to 73 years and participants had a variety of diagnoses. I recorded semi-structured interviews with participants. Data collection and analysis were iterative and followed theoretical sampling principles. FINDINGS In the (Dis)belief Model, I propose inaccessibility as the core concept. This refers to the private nature of pain that is inaccessible to others. I conceive of need drivers: motivating forces that seek to attain or protect something of value and avoid something not of value. The need drivers and the inaccessible character of pain drive the four process components in the model: pain expression, pain appraisal, belief expression and belief appraisal. Pain can be expressed or concealed. Individuals and others make sense of the pain and appraise its credibility. Those in pain encounter doubt, challenges, support, pain acknowledgement and professional (in)action. The appraisal of this behaviour as (dis)belief is affected by the individual’s underlying needs and is idiosyncratic. Finally, time and experience influence the (dis)belief phenomenon. CLINICAL IMPLICATIONS Based on the model, I propose six interactional approaches that might help clinicians communicate their belief in the patient’s pain. These are listening; being curious, unassuming and sensitive; mobilising resources; and managing expectations.