OBJECTIVES: Ankylosing spondylitis (prevalence 1% of population) is a chronic inflammatory progressive disease characterised by pain, joint stiffness, and gradual loss of mobility leading to severe functional impairment. There are no cost-of-illness data available in Czech Republic or in Eastern Europe. To assess direct and indirect costs of ankylosing spondylitis we have analysed the data from a large patient cohort study. METHODS: Data of 1008 patients (average age 50.2 years) with ankylosing spondylitis were analysed. Patients were enrolled in a patientxs organisation survey named BÉÏA. Data on health care consumption and productivity loss were collected. For calculation of indirect cost the friction cost approach was applied. RESULTS: The average time from diagnosis was 23 years; 61% were male. Two thirds of patients were disabled and unable to work. The mean annual direct cost per patient is estimated at 1259 EUR (49%) and the indirect cost due to lost work capacity is 1314 EUR (51%). The major contributors to the total direct costs were physiotherapy, spa and rehabilitation clinics (67% of direct costs). Drug treatment contributed to 22% and hospital admissions to 5% of direct costs. CONCLUSION: The annual total direct plus indirect costs of one patient with ankylosing spondylitis in Czech Republic were 2573 EUR. The share of direct and indirect costs was almost equal. Our findings provide information on the burden of disease and a baseline for cost-effectiveness evaluation of new costly treatments.