Most analyses of the economic benefits of smoking cessation consider long-term effects, which are often not of interest to public and private policy makers. These analyses fail to account for the time course of the short-run cost savings from the rapid decline in risk of acute myocardial infarction (AMI) and stroke. We estimate the time course of the fall in risk of AMI and stroke after smoking cessation and simulate the impact of a 1% absolute reduction in smoking prevalence on the number of and short-term direct medical costs associated with the prevented AMIs and strokes. In the first year, there would be 924+/-679 (mean+/-SD) fewer hospitalizations for AMI and 538+/-508 for stroke, resulting in an immediate savings of $44+/-26 million. A 7-year program that reduced smoking prevalence by 1% per year would result in a total of 63,840+/-15,521 fewer hospitalizations for AMI and 34,261+/-9133 fewer for stroke, resulting in a total savings of $3.20+/-0.59 billion in costs, and would prevent approximately 13,100 deaths resulting from AMI that occur before people reach the hospital. Creating a new nonsmoker reduces anticipated medical costs associated with AMI and stroke by $47 in the first year and by $853 during the next 7 years (discounting 2.5% per year). Although primary prevention of smoking among teenagers is important, reducing adult smoking pays more immediate dividends, both in terms of health improvements and cost savings.