The clinical features of 35 female patients with ankylosing spondylitis were compared with 70 male controls individually matched for disease duration. Mean age of onset and presenting symptoms were similar in both groups. No differences were observed as regards spinal symptoms, chest expansion, peripheral arthritis, extraarticular features or functional outcome. However, males had significantly greater spinal radiological change that was positively associated with hip arthritis. Our findings suggest that although axial disease is more severe in males the overall pattern of clinical disease is similar in both sexes.