A randomized, controlled, malaria-clinic-based field trial was carried out to compare the cost-effectiveness of a 5-day 700-mg oral artesunate and a 7-day quinine + tetracycline regimen for the treatment of uncomplicated falciparum malaria in Thailand. Cost-effectiveness was determined from the providers' perspective and based on curativeeffectiveness. A total of 137 patients, aged 15±60 years, attending a malaria clinic were followed for 28 days, 60 of them received quinine + tetracycline and 77 received artesunate. Cure rates were assessed on day 5 (artesunate) and day 7 (quinine + tetracycline), using the intention-to-treat approach. Cost-effectiveness and sensitivity analyses were performed by varying the day 5/day 7 curative effectiveness and cost of artesunate. The cure rate with artesunate (100%) was significantly higher than with quinine + tetracycline (77.4%) (relative risk adjusted for sex (aRR) = 1. 32, 95% confidence interval (Cl) = 1.12±1.55; referent quinine + tetracycline). Artesunate was more cost-effective than quinine + tetracycline at the following costs: artesunate,4US$ 0.36 per 50-mg tablet; quinine, US$ 0.06 per 300-mg tablet; tetracycline, US$ 0.02 per 250-mg capsule; and services per case found,4US$ 11.49. Because of the higher cure rate and higher cost-effectiveness of the artesunate regimen compared with quinine + tetracycline, we recommend its use for the treatment of uncomplicated falciparum malaria in malaria clinics in Thailand