We examined the sera of 50 patients with anterior uveitis (AU) for the presence of interferon and neopterin, an interferon induced pteridine derivative. Neopterin release is induced by gamma interferon and it is a more stable compound. Our results indicate that although there is no detectable differences in serum interferon levels between patients and controls, neopterin levels were elevated in patients with active disease, possibly indicating a localised activation of the interferon system.