Arachnoid ossificans is a rare type of chronic arachnoiditis characterised by the presence of calcification or ossification of the dura and arachnoid. There are a few reports of these findings in relation to various disease entities, but only one case has been reported in relation to ankylosing spondylitis. We describe a 76-year-old man of ankylosing spondylitis with arachnoiditis ossificans, who has suffered from low back pain and neuropathic leg pain.