Despite its low cost and its proven efficacy in prevention of recurrence of ischemic events, acetylsalicylic acid is in France a strategy not used as frequently as it should be. In order to convince practitioners and public authorities, we provide a cost-effectiveness analysis (CEA) of lysine acetylsalicylate (LA) 300 mg as compared to “do nothing”. We used Garber and Phelps’s specification of CEA. Efficacy data were derived from the Antiplatelet Trialists’ Collaboration meta-analysis. We used French data sources to estimate the cost of the prophylactic treatment, the cost of treatment-related side effects, and the cost of non fatal events to be prevented (ischemic stroke, myocardial infarction). The perspective taken into account for this CEA is that of the French Social Security system. Cost-effectiveness ratios (1996 US$) Qualifying event Endpoint MI Ischemic stroke Unstable angina -5,703 190,711* Prior MI -15 -37 Prior ischemic stroke -610 -176 Stable angina 4,375 15,749* *Insignificant difference in efficacy between LA and placebo These results provide economic evidence of the interest of lysine acetylsalicylate in preventing ischemic accidents since the benefits produced by the prophylactic treatment almost exceed the costs induced by this strategy. As a consequence, such negative net costs induce savings for the Social Security system. Therefore the prescription of acetylsalicylic acid and in particular lysine acetylsalicylate is medically effective and economically efficient.