Background: Exploration of values and preferences in the context of anticoagulation therapy for atrial fibrillation (AF) remains limited. To better characterize the distribution of patient and physician values and preferences relevant to decisions regarding anticoagulation in patients with AF, we conducted interviews with patients at risk of developing AF and physicians who manage patients with AF. Methods: We interviewed 96 outpatients and 96 physicians in a multicenter study and elicited the maximal increased risk of bleeding (threshold risk) that respondents would tolerate with warfarin vs. aspirin to achieve a reduction in three strokes in 100 patients over a 2-year period. We used the probabilistic version of the threshold technique. Results: The median threshold risk for both patients and physicians was 10 additional bleeds (10 P = 0.7). In both groups, we observed large variability in the threshold number of bleeds, with wider variability in patients than clinicians [patient range: 0-100, physician range: 0-50]. We observed one cluster of patients and physicians who would tolerate <10 bleeds and another cluster of patients, but not physicians, who would accept more than 35. Conclusions: Our findings suggest wide variability in patient and physician values and preferences regarding the trade-off between strokes and bleeds. Results suggest that in individual decision making, physician and patient values and preferences will often be discordant; this mandates tailoring treatment to the individual patient's preferences.