OBJECTIVES: The cost-effectiveness of the Swedish quitline, a nation-wide, free of charge service, is assessed. METHODS: The study was based on data of a sample of 1131 callers enrolled from February 1, 2000 to November 30, 2001. Outcome was measured as cost per quitter and cost per year of life saved. Cost per quitter was based on a calculation of the total cost of the quitline divided by the number of individuals who reported abstinence after 12 months. The cost per life year saved (LYS) was calculated by the use of data from the literature on average life expectancy for smokers versus quitters, the total cost of the quitline, and the cost of pharmacological treatment. RESULTS: The number of smokers who used the quitline and reported abstinence after 1 year was 354 (31 percent). The accumulated number of life years saved in the study population was 2400. The cost per quitter was 1052-1360 USD, and the cost per life year saved was 311-401 USD. A sensitivity analysis showed that, for outcomes down to an abstinence rate of 20 percent, the cost per LYS rose modestly, from 311 to 482 USD. Discounting the cost per LYS showed the cost to be 135 USD for 3 percent and 283 USD for 5 percent. CONCLUSIONS: The Swedish quitline is a cost-effective public health intervention compared with other smoking cessation interventions.