Haemorrhoidal disease (HD) is one of the most common diseases encountered by the clinicians of general surgery. Chronic constipation, pushing during defecation and increased abdominal pressure play an important role in development of haemorrhoidal disease. Patients with ankylosing spondylitis (AS) frequently use the Valsalva manoeuvre in their daily lives, which may increase the abdominal pressure, leading to formation of haemorrhoids. The purpose of this study was to evaluate the incidence of haemorrhoidal disease in patients with AS. A total of 221 individuals were included in this study in three groups as follows: 72 patients with ankylosing spondylitis (AS), 75 patients with chronic low back pain (LBP) and 74 healthy control subjects. Patients were examined both physically and anoscopically, and their histories were taken. The incidence of HD was 45.8% in patients with AS, 16% in patients with chronic LBP and 9.5% in healthy control subjects. The incidence of HD was significantly higher in patients with AS compared to the other groups. Patients with AS have a high incidence of HD, which should be taken into consideration by clinicians during routine examination of these patients.