PURPOSE To compare the clinical features and outcomes of HLA-B27-positive and HLA-B27-negative acute anterior uveitis (AAU) in a large Turkish patient population. METHODS Forty-four patients with HLA-B27-positive AAU and 65 with HLA-B27-negative AAU were reviewed retrospectively. HLA-B27 typing, gender, laterality, clinical features (fibrinous reaction, hypopyon formation), ocular complications, medical treatment, and final visual acuity were recorded. Statistical analyses included Student's t-test, Fisher's exact test, Yate's corrected Chi2 test, and Mann-Whitney U test. A p-value of <0.05 was considered statistically significant. RESULTS Forty percent of all patients with AAU were found to be positive for HLA-B27 antigen. HLA-B27-positive AAU was significantly more common in males and HLA-B27-negative AAU in females. Unilateral or bilateral alternating AAU as well as fibrinous reaction and hypopyon formation were more common in HLA-B27-positive patients. Posterior iris synechiae and cataract formation were more common and systemic immunosuppressive agents were exclusively required in patients with HLA-B27-negative AAU. Visual outcome did not differ significantly between the HLA-B27-positive and HLA-B27-negative groups. CONCLUSIONS HLA-B27 association is less common in Turkish patients with AAU than in other populations reported in the literature. Although distinct features of HLA-B27 uveitis were confirmed in our study, visual outcome did not differ from idiopathic AAU. Therefore, we believe that HLA-B27 typing in patients with AAU helps the clinician with the diagnosis. However, it has a limited value in determining the prognosis.