Objectives: To describe the perspectives of clinicians and researchers on identifying, establishing and implementing core outcomes in haemodialysis and their expected impact. / Design: Face-to-face, semistructured interviews; thematic analysis. / Stetting: Twenty-seven centres across nine countries. / Participants: Fifty-eight nephrologists (42 (72%) who were also triallists). / Results: We identified six themes: reflecting direct patient relevance and impact (survival as the primary goal of dialysis, enabling well-being and functioning, severe consequences of comorbidities and complications, indicators of treatment success, universal relevance, stakeholder consensus); amenable and responsive to interventions (realistic and possible to intervene on, differentiating between treatments); reflective of economic burden on healthcare; feasibility of implementation (clarity and consistency in definition, easily measurable, requiring minimal resources, creating a cultural shift, aversion to intensifying bureaucracy, allowing justifiable exceptions); authoritative inducement and directive (endorsement for legitimacy, necessity of buy-in from dialysis providers, incentivising uptake); instituting patient-centredness (explicitly addressing patient-important outcomes, reciprocating trial participation, improving comparability of interventions for decision-making, driving quality improvement and compelling a focus on quality of life). / Conclusions: Nephrologists emphasised that core outcomes should be relevant to patients, amenable to change, feasible to implement and supported by stakeholder organisations. They expected core outcomes would improve patient-centred care and outcomes