An analysis was made of 1309 patients with uveitis seen at University Hospitals participating in the Uveitis Centre of the Netherlands Ophthalmic Research Institute. In this series B27-associated anterior uveitis was the most frequent entity (18%) followed by Toxoplasma chorioretinitis (7%). Sarcoid uveitis, pars planitis and Fuchs' heterochromic cyclitis each accounted for approximately 4-5% of cases. In 44% of the patients no specific diagnosis could be made. Central diagnosis registration is of great importance when conducting clinical uveitis research.