The aim of this study is to assess the trends in work disability and sick leave in ankylosing spondylitis (AS). In 1993 and 2007, patients diagnosed with AS that attended to a secondary- or a tertiary-care outpatient rheumatology clinics were evaluated for demographics, disease characteristics, axial mobility, working status, and work days missed due to sick leave or permanent disability. Factors that impacted labor status were identified by multiple regression analysis. In 1993, 91 study individuals (mean age 35 years, mean disease duration 10 ± 8 years) included 28 (31%) on permanent disability and 63 currently working; of these 63, 42 (67%) had missed at least 1 work day in the previous 12 months (mean 69 ± 63 days). In the next 5 years, the annual permanent disability was 3%. In 2007, 185 study individuals (mean age 42, mean disease duration 12 ± 10 years) included 53 (39%) on permanent disability and 132 active workers; 35 (66%) out of the 53 began permanent disability between 1999 and 2007 (2.1% annual disability rate), and 53 (40%) out of 132 active workers missed at least 1 work day in the previous 12 months (mean 52 ± 63 days). Only age predicted disability, with 10% and 11% increases in risk per year in 1993 and 2007, respectively (hazard ratios 1.09 and 1.11, respectively; p = 0.03 for both). Although the impact of AS on work seems to decrease slightly during the last 15 years, the actual impact is still substantial. An important proportion of patients went on permanent disability in the three decades before retirement. Extrapolating these results to official data for the year 2005, we may infer that between 1.3 million and nearly 15 million working days were missed that year due to AS.