Background and AimsAnkylosing spondylitis (AS) is a multisystem disorder with ocular, pulmonary, and cardiovascular involvement. The incidence of pulmonary involvement varies from 1 to 52%. Abnormal T-cell function-derived immune responses are involved in AS pathogenesis. Numerous genes such as CTLA4 and CD28 control T-cell functions. In this study, we aimed to address the relationship between CTLA4 and CD28 polymorphisms and lung involvement in Turkish patients with AS.