Purpose-Idiopathic uveitis is frequently the most common diagnosis in series from uveitis clinics. We sought to determine the percentage of patients initially diagnosed as idiopathic, noninfectious uveitis referred to a tertiary uveitis center who were subsequently found to have an identifiable cause of uveitis. Design-Retrospective case series. Methods-We performed a computerized database analysis of 179 consecutive patients who were referred to our practice with the diagnosis of idiopathic, non-infectious uveitis between 2008 and 2016. Patients were evaluated by a thorough history and ophthalmic examination with selected laboratory testing targeted by clues from the history and exam. Standardization of Uveitis Nomenclature (SUN) criteria 1 were used to better assess different types of uveitis. Results-Fifty-two out of 179 (29.0%) patients initially diagnosed with idiopathic uveitis were subsequently diagnosed with an underlying condition. Among patients referred with a diagnosis of idiopathic disease, females were most commonly affected with 121/179 (67.6%). Among subsequent diagnoses, sarcoidosis was the most common (19/52 or 36.5%), followed by HLA-B27 associated uveitis (11/52, 21.1%), infectious (6/52,11.5%), tubulo-interstitial nephritis with uveitis (6/52, 11.5%), and juvenile idiopathic uveitis (4/52, 7.7%). Other diagnosable conditions included Behcet's disease, multifocal choroiditis and pan-uveitis, Crohn's disease, multiple sclerosis, and relapsing polychondritis. An underlying condition was not found in 127/179 (70.9%) patients.