To report the interim 34-week safety and efficacy results of a 3-year study to evaluate an investigational intravitreal fluocinolone acetonide (FA) implant in patients with noninfectious posterior uveitis. Prospective, dose-masked, dose-randomized, historically controlled, multicenter trial in patients with unilateral or bilateral disease. A total of 278 patients with recurrent noninfectious posterior uveitis were randomized to receive a 0.59-mg (n = 110) or 2.1-mg (n = 168) implant. In patients with bilateral disease, the more severely affected eye received the implant. The implant was inserted surgically into the vitreous cavity through a pars plana incision. Follow-up visits were scheduled on day 2, week 1, and then every 4 to 6 weeks through 34 weeks after implantation. Systemic, periocular, and topical therapies were reduced as allowed by the clinical response. The primary efficacy outcome was a comparison of the recurrence rate in the implanted eye from the 34 weeks before implantation to the 34 weeks after implantation. Visual acuity (VA), need for adjunctive therapy, and safety also were assessed. Combining both doses, the FA implant reduced the rate of recurrences from 51.4% in the 34 weeks preceding implantation to 6.1% postimplantation (P or =2 grades in 19.8% of phakic implanted eyes, and 9.9% required cataract surgery. There were no statistically significant differences in any of the parameters studied for the 0.59-mg implant, compared with the 2.1-mg implant. The FA implant significantly reduced uveitis recurrences, improved VA, and decreased the need for adjunctive therapy in the studied patient population. The most common side effects included increased intraocular pressure and cataract progression.