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Chemoprophylaxis for thromboembolism is a controversial topic in plastic surgery today. Surveys reveal a reluctance among plastic sur-geons to adopt anticoagulation in their practices.1 Proponents ask, which problem would you rather treat, a hematoma or a thromboembolism?2,3 Efforts to reduce the risk of venous thromboem-bolism are understandable. The seriousness of this complication is unquestioned. Why then the reluc-tance to incorporate chemoprophylaxis in one’s practice? The issue is not just medical, but ethical. Despite the ethical principles at stake, there has been no discussion of them in our literature. We would do well to submit this issue to a critical analysis that in-cludes ethical considerations.4 The dilemma is a classic example of the double-effect principle—the intervention is both good and bad. This ethical conundrum is hardly new or specif-ic to plastic surgery. It was first considered by Thom-as Aquinas.5 The ethical criteria are summarized as follows6: 1. That the action in itself from its very object be good or at least indifferent. 2. That the good effect and not the evil effect be intended. 3. That the good effect be not produced by means of the evil effect. 4. That there be a proportionately grave reason for permitting the evil effect. To be morally justified, these conditions must be met. An example is the use of vaccines. A vaccine would never be approved if as many people died from the side effects as were saved by prevention of the targeted disease. THAT THE ACTION IN ITSELF BE GOOD First, the benefit must be clear. Perhaps surpris-ingly, this bar has not been met conclusively for plas-tic surgery outpatients. Guidelines provided by the American College of Chest Physicians cannot be reli-ably extrapolated to plastic surgery because of the dif-ferences in patient characteristics, presence of serious diseases, and types of surgery (W.H. Geerts, persona