ObjectivesThe Outcome Measures in Rheumatology Initiative established the Contextual Factors Working Group to guide the understanding, identification and handling of contextual factors for clinical trials. In clinical research, different uses of the term ‘contextual factors’ exist. This study explores the perspectives of researchers (including clinicians) and patients in defining 'contextual factor’ and its related terminology, identifying such factors and accounting for them in trials across rheumatology.MethodsWe conducted individual semistructured interviews with researchers (including clinicians) who have experience within the field of contextual factors in clinical trials or other potentially relevant areas, and small focus group interviews with patients with rheumatic conditions. We transcribed the interviews and applied qualitative content analysis.ResultsWe interviewed 12 researchers and 7 patients. Researcher's and patient's descriptions of contextual factors were categorised into two broad themes, each comprising two contextual factors types. The ‘treatment effect’ theme focused on factors explaining variations in treatment effects (A) among patients and (B) among studies. The ‘outcome measurement’ theme focused on factors that explain (C) variations in the measurement result itself (apart from actual changes/differences in the outcome) and (D) variations in the outcome itself (beside treatment of interest). Methods for identifying and handling contextual factors differed among these themes and types.ConclusionsTwo main themes for contextual factors with four types of contextual factors were identified based on input from researchers and patients. This will guide operationalisation of contextual factors. Further research should refine our findings and establish consensus among relevant stakeholders.