Forty-four females and 82 male patients with ankylosing spondylitis (AS) were compared in a retrospective study. No differences were found with respect to age at onset of disease, initial symptoms, work performance or peripheral joint involvement. Furthermore, males and females did not differ in restriction of spinal mobility, chest expansion, frequency of acute anterior uveitis or mean concentration of IgA. Males had significantly higher frequency of elevated C-reactive protein whereas mean erythrocyte sedimentation rate showed no such difference.