Purpose: To evaluate the incidence of optic neuritis (ON) in patients using anti-tumor necrosis factor (TNF) alpha therapy. Design: Retrospective, population-based cohort study. Methods: We identified new users of anti-TNF therapy (etanercept, infliximab, or adalimumab) or nonbiologic disease-modifying antirheumatic drugs (DMARDs) during 2000-2007 from the following data sources: Kaiser Permanente Northern California, Pharmaceutical Assistance Contract for the Elderly, Tennessee Medicaid, and National Medicaid/Medicare. Within this cohort, we used validated algorithms to identify ON cases occurring after onset of new drug exposure. We then calculated and compared ON incidence rates between exposure groups. Results: We identified 61 227 eligible inflammatory disease patients with either new anti-TNF or new nonbiologic DMARD use. Among this cohort, we found 3 ON cases among anti-TNF new users, occurring a median of 123 days (range, 37-221 days) after anti-TNF start. The crude incidence rate of ON across all disease indications among anti-TNF new users was 10.4 (95% CI 3.3-32.2) cases per 100 000 person-years. In a sensitivity analysis considering current or past anti-TNF or DMARD use, we identified a total of 6 ON cases: 3 among anti-TNF users and 3 among DMARD users. Crude ON rates were similar among anti-TNF and DMARD groups: 4.5 (95% CI 1.4-13.8) and 5.4 (95% CI 1.7-16.6) per 100 000 person-years, respectively. Conclusion: Optic neuritis is rare among those who initiate anti-TNF therapy and occurs with similar frequency among those with nonbiologic DMARD exposure. © 2013 Elsevier Inc.