Of 340 patients with anterior uveitis, 20 (6%) had diabetes mellitus. This is significantly higher than the prevalence of 1.4% in the normal Dutch population (P less than .001). Of 128 patients with idiopathic anterior uveitis, 16 (12.5%) had diabetes mellitus compared to only four (1.9%) of 212 patients with anterior uveitis with an established specific ocular diagnosis (P less than .001). Of the 16 diabetic patients with idiopathic anterior uveitis, ten (63%) had type I diabetes mellitus and 12 (75%) suffered from severe diabetic complications as angiopathy, nephropathy, and neuropathy. The onset of diabetes mellitus preceded the onset of anterior uveitis in all cases. Whether or not uveitis in diabetic patients is a true inflammation rather than an ischemic phenomenon is still unknown.