Anterior uveitis is a common inflammatory eye disease associated with the HLA-B27 phenotype. Bacteriologic cofactors have been implicated in the pathogenesis of several diseases associated with HLA-B27. Using a sensitive enzyme-linked immunosorbent assay, we examined the incidence of previous Yersinia infection in a group of 28 consecutive patients with anterior uveitis. Twelve patients had a significantly increased antibody response to Yersinia, 8 of whom were HLA-B27 positive. Eight patients had IgM antibodies, possibly indicative of recent infection. There were no positive Yersinia serologic findings in our control group of 28 subjects, 13 of whom were HLA-B27 positive. A strong association was found between previous Yersinia infection and the development of anterior uveitis in HLA-B27-positive and HLA-B27-negative patients.