PURPOSE: To evaluate treatment outcomes of azathioprine for noninfectious ocular inflammatory diseases. DESIGN: Retrospective cohort study. METHODS: Medical records of 145 patients starting azathioprine as a sole noncorticosteroid immunosuppressant at 4 tertiary uveitis services were reviewed. Main outcome measures included control of ocular inflammation, sustained control after tapering prednisone to </= 10 mg/day, and discontinuation of treatment because of side effects. RESULTS: Among 145 patients (255 eyes) treated with azathioprine, 63% had uveitis, 23% had mucous membrane pemphigoid, 11% had scleritis, and 3% had other inflammatory diseases. By Kaplan-Meier analysis, 62% (95% confidence interval [CI], 50% to 74%) of patients with active disease initially gained complete inactivity of inflammation sustained over at least 28 days within 1 year of therapy, and 47% (95% CI, 37% to 58%) tapered systemic corticosteroids to </= 10 mg daily while maintaining control of inflammation within 1 year of therapy. Treatment success was most common for intermediate uveitis (90% with sustained inactivity within 1 year; 95% CI, 64% to 99%). Over the median follow-up of 230 days (interquartile range, 62 to 679 days), azathioprine was discontinued at a rate of 0.45 per person-years (/PY): 0.16/PY because of side effects, 0.10/PY because of ineffectiveness, 0.09/PY because of disease remission, and 0.10/PY because of unspecified causes. CONCLUSIONS: Azathioprine was moderately effective as a single corticosteroid-sparing immunosuppressive agent in terms of control of inflammation and corticosteroid-sparing benefits, but required several months to achieve treatment goals; it seems especially useful for patients with intermediate uveitis. Treatment-limiting side effects occurred in approximately one-fourth of patients within 1 year, but typically were reversible.