Patient’s values and preferences regarding the relative importance of preventing strokes and avoiding bleeding are now recognised to be of great importance in deciding on therapy for the prevention of stroke due to atrial fibrillation (SPAF). We used an iPad questionnaire to determine the minimal clinically important difference (Treatment Threshold) and the maximum number of major bleeding events that a patient would be willing to endure in order to prevent one stroke (Bleeding Ratio) for the initiation of antithrombotic therapy in 172 hospital in-patients with documented non-valvular atrial fibrillation in whom anticoagulant therapy was being considered. Patients expressed strong opinions regarding SPAF. We found that 12% of patients were “medication averse” and were not willing to consider antithrombotic therapy; even if it was 100% effective in preventing strokes. Of those patients who were willing to consider antithrombotic therapy, 42% were identified as “risk averse” and 15% were “risk tolerant”. Patients required at least a 0.8% (NNT=125) annual absolute risk reduction and 15% relative risk reduction in the risk of stroke in order to agree to initiate antithrombotic therapy, and patients were willing to endure 4.4 major bleeds in order to prevent one stroke. In conclusion, there was a substantial amount of inter-patient variability, and often extreme differences in opinion regarding tolerance of bleeding risk in the context of stroke prevention in atrial fibrillation. These findings highlight the importance of considering patient preferences when deciding on SPAF therapy.