Aspirin exerts antiplatelet effects through irreversible inhibition of cyclooxygenase-1, whereas its anticancer effects may be due to inhibition of cyclooxygenase-2 and other pathways. In 2009, the U.S. Preventive Services Task Force endorsed aspirin for primary prevention of cardiovascular disease. However, aspirin's role in cancer prevention is still emerging, and no groups currently recommend its use for this purpose. To help physicians balance the benefits and harms of aspirin in primary disease prevention, the Task Force issued a guideline titled, "Aspirin Use for the Primary Prevention of Cardiovascular Disease and Colorectal Cancer" in 2016. In the evidence review conducted for the guideline, cardiovascular disease mortality and colorectal cancer mortality were significantly reduced among persons taking aspirin. However, there was no difference in nonfatal stroke, cardiovascular disease mortality, or all-cause mortality, nor in total cancer mortality, among those taking aspirin. Aspirin users were found to be at increased risk for major gastrointestinal bleeding. In this Beyond the Guidelines, the guideline is reviewed and 2 experts discuss how they would apply it to a 57-year-old man considering starting aspirin for primary prevention. Our experts review the data on which the guideline is based, discuss how they would balance the benefits and harms of aspirin therapy, and explain how they would incorporate shared decision making into clinical practice.