Background & Aims: Eosinophilic esophagitis is an increasingly recognized disorder with distinctive endoscopic, histologic, and allergic features. Although several therapies are advocated, no placebo-controlled trials have been conducted. We aimed to determine the efficacy of swallowed fluticasone propionate (FP) in the treatment of eosinophilic esophagitis. Methods: We conducted a randomized, double-blind, placebo-controlled trial of swallowed FP in pediatric patients with active eosinophilic esophagitis. Thirty-six patients were randomly assigned to receive either 880 μg of FP (21 patients) or placebo (15 patients) divided twice daily for 3 months. The primary end point was histologic remission, defined by a peak eosinophil count of ≤1 eosinophil in all 400× fields in both the proximal and distal esophagus. Results: Fifty percent of FP-treated patients achieved histologic remission compared with 9% of patients receiving placebo ( P = .047). FP decreased esophageal eosinophil levels, with a more pronounced effect in nonallergic individuals (65.9 ± 25.3 vs 1.4 ± 1.1 eosinophils/high-power field in the proximal esophagus [ P = .03] and 84.6 ± 19.7 vs 19.6 ± 12.9 eosinophils/high-power field in the distal esophagus [ P = .04]). Resolution of vomiting occurred more frequently with FP than placebo (67% vs 27%; P = .04). FP-induced resolution of mucosal eosinophilia was associated with resolution of endoscopic findings, epithelial hyperplasia, younger age ( P = .0003), shorter height ( P = .002), and lighter weight ( P = .02). Effective treatment with FP decreased the number of CD8 + T lymphocytes and mast cells in both the proximal and distal esophagus ( P < .05). Conclusions: Swallowed FP is effective in inducing histologic remission in eosinophilic esophagitis, with a more pronounced effect in nonallergic and younger individuals, especially in the proximal esophagus.