Background Cancer patients are at risk of developing blood clots in their veins - venous thromboembolism - which often takes the form of a pulmonary embolism or deep vein thrombosis. The risk increases with advanced disease. Evidence based treatment is low molecular weight heparin by daily subcutaneous injection. The aim of this research is to explore the barriers for doctors in the UK when diagnosing and treating advanced cancer patients with VTE. Method Qualitative, in-depth interview study with 45 doctors. Doctors (...) were from three specialties: oncology, palliative medicine and general practice, with a mixture of senior and junior staff. Framework analysis was used. Results Doctors opinions as to whether LMWH treatment was ethically appropriate for patients who were symptomatic from VTE but at end of life existed on a shifting continuum, largely influenced by patient prognosis. A lack of immediate benefit coupled with the discomfort of a daily injection had influenced some doctors not to prescribe LMWH. The point at which LMWH injections should be stopped in patients at the end of life was ambiguous_._ Some perceived ‘overcaution’ in their own and other clinicians’ treatment of patients_._ Viewpoints were divergent on whether dying of a PE was considered a “good way to go”. The interventionalism and ethos of palliative medicine was discussed. Conclusions Decisions are difficult for doctors to make regarding LMWH treatment for advanced cancer patients with VTE. Treatment for this patient group is bounded to the doctors own moral and ethical frameworks. (shrink)