The tissue antigen HLA-B27 is found in 50% of Dutch acute anterior uveitis (AAU) patients. The prevalence of HLA-B27 in the normal population is only 8%. However, only approximately 1% of HLA-B27+ individuals will develop AAU. Therefore, it is possible that the disease is associated with a particular B27 subtype. We typed lymphocytes of 36 B27+ AAU patients, of which 20 also had ankylosing spondylitis, for three serologically defined B27 subtypes (B27 W, B27 K and B27 non W/non K). These subtypes were normally associated with AAU. The subtype frequencies in the patients suffering from both AAU and AS also showed no preference for a certain subtype. Subtype-specific characteristics of the primary structure of the various B27 subtype molecules therefore cannot be responsible for the disease association.