OBJECTIVES: Estimate risk-adjusted healthcare costs and identify associated risk factors for ankylosing spondylitis (AS) expenditures in Turkey using real-world data. METHODS: Research-identified data from a system that processes claims for all Turkish health insurance funds was analyzed. Adult prevalent AS patients with two AS visits at least 60 days apart, identified between June 1, 2010 and December 31, 2010, were required to have an AS diagnosis before June 1, 2010, with at least 1 year of continuous enrollment for the baseline and follow-up years. Pharmacy, outpatient and inpatient claims were compiled over the study period for the selected patients. RESULTS: Among 2,383 patients (mean age: 40.52; female: 38%), 51% were age 18-39, 46% were 40-64 years and 3% were age 65 or older. AS diagnoses were most prevalent in the Marmara region (46%), followed by Aegean (17%), Central Anatolia (22%), and Mediterranean (8%).  Nearly 40% of AS patients had at least one cardiovascular, diabetic, respiratory, allergy, Crohn's disease, uveit and rheumatoid arthritis comorbid condition prior to AS diagnosis. 7% of patients were hospitalized and 46% had at least one outpatient visit during the pre-index period. Most patients were prescribed non-COX inhibitors (71%) and 35% of patients were prescribed disease-modifying anti-rheumatic drugs (DMARDs).  Few patients (1%) had surgery prior to diagnosis.  The total annual cost (ª4,233) was comprised of mainly pharmacy (ª3,760), followed by outpatient (ª297), and inpatient costs (ª155), and an average copay of ª21.  Prior comorbid conditions including diabetes, respiratory disease as well as hospitalization, glucocorticoid and DMARD use significantly contributed to annual healthcare costs, unlike gender and age. CONCLUSIONS: Annual costs of AS patients are significantly lower in Turkey relative to other European countries, yet, pharmaceutical expenditures cover a significant portion of the overall cost. Comparative effectiveness studies are needed to further decrease pharmaceutical expenditures for AS treatment.