Twenty-six patients with acute anterior uveitis associated with HLA-B27 antigen were compared with 31 patients with acute anterior uveitis HLA-B27 negative. No statistical difference was found in the clinical picture of both groups except for the occurrence of unilateral or bilateral involvement. Almost all patients with bilateral eye involvement were HLA-B27 negative and had no evidence of systemic disease, while unilateral involvement occurred in both groups of HLA-B27 positive and negative patients.