OBJECTIVE: The aim of this study was to identify characteristics associated with the presence and development of extra-articular manifestations (EAMs) in a prevalence cohort of patients with AS. METHODS: Twelve-year follow-up data from the Outcome in Ankylosing Spondylitis International Study (OASIS) were used. In addition, medical charts were checked for the presence of acute anterior uveitis (AAU), IBD and psoriasis. Demographic, clinical and radiographic characteristics associated with the presence of (any) EAM at baseline or new development during follow-up were identified. RESULTS: Two hundred and sixteen patients were included [mean age 43.6 years (s.d. 12.7), 154 (71%) men, mean symptom duration 20.5 years (s.d. 11.7), mean follow-up 8.3 years (s.d. 4.3)]. At baseline, 39 (18%) patients had AAU, 15 (7%) had IBD and 9 (4%) had psoriasis. The history of AAU was univariably associated with increased age [odds ratio (OR) 1.04 (95% CI 1.01, 1.07)], longer symptom duration [OR 1.05 (95% CI 1.02, 1.08)] and more radiographic damage [OR 1.02 (95% CI 1.00, 1.04)]. The history of psoriasis was associated with greater age [OR 1.05 (95% CI 1.00, 1.11)] and lower CRP [OR 0.77 (95% CI 0.59, 1.00)]. At follow-up, 27 patients developed a new EAM. Newly developed IBD was associated with a higher time-varying AS Disease Activity Score [hazard ratio (HR) 2.80 (95% CI 1.43, 5.52)], worse physical function [HR 1.40 (95% CI 1.09, 1.80)] and worse patient global well-being [HR 1.46 (95% CI 1.10, 1.93)]. Newly developed AAU was associated with an elevated time-varying CRP [HR 1.02 (95% CI 1.01, 1.04)]. CONCLUSION: Development of EAMs was infrequent in this cohort, despite relatively long follow-up. In particular, markers of disease activity were associated with the development of IBD.