OBJECTIVES Chronic obstructive pulmonary disease (COPD) has a prevalence of 9.1% in Spain. Exacerbation is one of the most important cost drivers in COPD. The purpose of this analysis was to assess the cost-effectiveness of tiotropium, a once daily inhaled anticholinergic. METHODS A cost-effectiveness analysis has been performed, defining effectiveness as each exacerbation avoided. Effectiveness data of tiotropium and comparator have been obtained from a one-year clinical trial comparing tiotropium plus standard treatment (short-acting beta-adrenergic and/or inhaled/oral corticoids) with placebo plus standard treatment (defined as above), which showed that the group receiving tiotropium had less exacerbations per year (1.57 vs 2.41; p <0.01)1 Healthcare resources utilization has been taken from the same clinical trial, a systematic review of the literature, and a local expert panel. The analysis has only included direct medical costs from the perspective of the Spanish National Health System. Drug costs were taken from an official source and other costs from a Spanish healthcare cost database, both dated 2005. The time horizon selected was one year, the follow-up period of the aforementioned clinical trial. RESULTS Total costs per patient in the tiotropium group was 1,388 € and in the placebo group 1,119 €. Hospitalisation costs accounted for 44% and 84% in the tiotropium and placebo group, respectively. The incremental cost-effectiveness ratio was 320 € to prevent one exacerbation in a COPD patient when using tiotropium instead of placebo. CONCLUSIONS The use of tiotropium in addition to the standard treatment as defined in the clinical trial from which effectiveness data were derived is a cost-effective measure in the management of patients with COPD in Spain. 1MISTRAL study – Eur Resp J 2004; 24 (Suppl 48): 513s