We used the following calculations to estimate the annual risk of nonfatal stroke (ie, ischemic and hemorrhagic) on aspirin: (1) multiplication of reported rates of ischemic stroke by 1.08 to account for additional hemorrhagic strokes on aspirin therapy (based on the observed ratio of ischemic:hemorrhagic strokes in aspirin arms of RCTs in patients with AF) and (2) an estimation that 50% and 25% of hemorrhagic and ischemic strokes, respec- tively, were fatal. Depending on the clinical question being addressed by a par- ticular recommendation, we adjusted these absolute rates of nonfatal stroke on aspirin to re ect the clinical scenario being addressed. For the recommendation addressing VKA therapy vs no treatment, for example, to estimate absolute rates of non- fatal stroke on no treatment, we increased our estimates of the rate of nonfatal stroke on aspirin by 21% to account for the esti- mated ef cacy of aspirin in preventing stroke in AF). We there- fore used the following absolute rates of nonfatal stroke in untreated patients to develop our recommendations: 0.8%, 2.2%, 4.5%, and 9.6% per year for patients with CHADS2 scores of 0, 1, 2, and 3 to 6, respectively. We have chosen to base our treatment recommendations on absolute rates of stroke derived from clinical trials, recognizing that these data have important limitations. 