Background Since 2006 the Quality Outcomes Framework (QOF) has rewarded GPs for carrying out standardised assessments of the severity of symptoms of depression in newly diagnosed patients. Aim To gain understanding of GPs' opinions and perceived impact on practice of the routine introduction of standardised questionnaire measures of severity of depression through the UK general practice contract QOF. Design of study Semi-structured qualitative interview study, with purposive sampling and constant comparative analysis. Setting Thirty-four GPs from among 38 study general practices in three sites in England, UK: Southampton, Liverpool, and Norfolk. Method GPs were interviewed at a time convenient to them by trained interviewers. Interviews were audiorecorded and transcribed verbatim in preparation for thematic analysis, to identify key views. Results Analysis of the interviews suggested that the use of severity questionnaires posed an intrusion into the consultation. GPs discursively polarised two technologies: formal assessment versus personal enquiry, emphasising the need to ensure the scores are used sensitively and as an aid to clinical judgement rather than as a substitute. Importantly, these challenges implicitly served a function of preserving GPs' identities as professionals with expertise, constructed as integral to the process of diagnosis. Conclusion GP accounts indicated concern about threats to patient care. Contention between using severity questionnaires and delivering individualised patient care is significantly motivated by GP concerns to preserve professional expertise and identity. It is important to learn from GP concerns to help establish how best to optimise the use of severity questionnaires in depression.