To the Editor We read with interest the recent study of Cao et al1 examining the benefits of aspirin use over a range of doses and by subgroups. This study adds to the growing body of compelling evidence supporting long-term, low-dose aspirin chemoprevention for colorectal cancer. With respect to the authors’ concluding statement that cost-effectiveness analyses are warranted, we would add that several cost-effectiveness studies have been performed on this topic. In their Markov analyses, Pence et al2 concluded that aspirin with colonoscopy was more cost-effective at $12 950 per life-year saved than colonoscopy alone. In another study, Hassan et al3 observed that the cost-effectiveness of aspirin adjunct to colonoscopy was dependent on the risk of aspirin-related upper gastrointestinal bleeding and hemorrhagic stroke. In this model, the cost-effective benefit of aspirin with colonoscopy was lost when the efficacy of colonoscopy in preventing proximal colorectal cancer was increased from 56% to 73%.3