A prospective study was undertaken to investigate an apparent correlation between ankylosing spondylitis (AS) and the incidence of otological conditions. 42 consecutive patients attending the ankylosing spondylitis clinic were examined otoscopically and had audiometric assessment. 19% of the patients (8/42) had active or inactive chronic otitis media. The prevalence of chronic otitis media in this group was significantly greater (P < 0.01) than a stratified sample of the general population from the Medical Research Council Institute of Hearing Research National Study of Hearing, controlled for age, sex and socio-economic group, where the expected incidence was 5%. A hypothetical explanation for the association is given and the need for HLA studies into chronic otitis media is discussed.