Objective: To determine if a single intravitreal injection of 4 mg of triamcinolone acetonide in patients with classic choroidal neovascularization associated with agerelated macular degeneration can safely reduce the risk of severe visual loss. Methods: A double-masked, placebo-controlled, randomized clinical trial was performed in patients 60 years or older who had choroidal neovascularization with any classic component, a duration of symptoms of less than 1 year, and a visual acuity of 20/200 or better. Best corrected visual acuity, intraocular pressure, and cataract grading were performed before the injection and then at 3, 6, and 12 months. Main Outcome Measure: The development of severe loss of vision (30 letters) by survival analysis on an intention-to-treat basis. Results: One hundred fifty-one eyes were randomized into the study, and follow-up data were obtained for 73 (97%) of the 75 eyes in the treated group and for 70 (92%) of the 76 eyes in the control group. There was no difference between the 2 groups for the development of severe visual loss during the first year of the study (log-rank χ21=0.03, P=.90). In both groups, the 12-month risk of severe visual loss was 35%, with a hazard ratio of 1.05 (95% confidence interval, 0.59-1.86). The change in size of the neovascular membranes, however, was significantly less in eyes receiving triamcinolone than in those receiving placebo 3 months after treatment (P=.01), although no difference was noted after 12 months. After 12 months, treated eyes had a significantly higher risk of an elevated intraocular pressure (31/75 [41%] vs 3/76 [4%]; P<.001), but not of cataract progression (P=.29). Conclusions: A single dose of intravitreal triamcinolone had no effect on the risk of loss of visual acuity during the first year of the study in eyes with age-related macular degeneration and classic choroidal neovascularization, despite a significant antiangiogenic effect found 3 months after treatment. This biological effect warrants further study.