OBJECTIVES: Lifestyle changes to prevent type 2 diabetes among high-risk persons have been shown to be cost-effective. This study investigates the cost-effectiveness of a community-based program promoting general population lifestyle changes to prevent diabetes. METHODS: The 10-year program was implemented in three municipalities in Sweden. Effectiveness was measured with a quasiexperimental cohort design, that is, risk factor levels in a population group aged 36-56 years at baseline and 8-10 years later (2,149 men; 3,092 women) in the program municipalities and a control area were compared. The incremental cost-utility analysis included future diabetes and cardiovascular disease-related health effects and societal costs (discounted 3 percent), estimated by a Markov model. RESULTS: In all areas, risk factor levels increased during follow-up, leading to increased societal costs of between SEK40,000 and 90,000 (1 Euro 2004 = SEK9.13; 1 US$ = SEK 7.35) and quality-adjusted life-year (QALY) losses between 0.12 and 0.48 per individual. Compared with the control area, the cost increases and QALY losses for women were more favorable in two program areas but less favorable in one, and less favorable for men in both areas (data unavailable for one municipality). The findings indicate that the program was cost-effective in only two female study groups. CONCLUSIONS: Conflicting results on the cost-effectiveness of the program were obtained. As several potentially valuable aspects of the program are not included in the cost-effectiveness analysis, the societal value of the program might not be adequately reflected.