Lung transplant bronchiolitis obliterans syndrome (BOS) is the most significant long-term cause of morbidity and mortality after lung transplantation. Although augmented immunosuppression is used by most centers, reported on treatment to reverse BOS are largely anecdotal. We performed a double-blind, randomized, controlled trial (RCT) with ten treatment pairs of 2 weeks duration each comparing inhaled fluticasone propionate (2 x 1,000 micrograms/day) with placebo in a patient with BOS grade 2 who previously showed an improvement in lung function after inhaled steroids. The Baseline Dyspnea Index and the Modified Medical Research Council Dyspnea Scale showed a significant improvement during fluticasone treatment compared with the placebo period (2.7 +/- 0.2 vs. 2.0 +/- 0.3; p = 0.043; and 1.7 +/- 0.2 vs. 2.4 +/- 0.2; p = 0.043). The patient correctly identified fluticasone and placebo, respectively, in eight of ten trial pairs (p = 0.016). The values of forced expiratory volume in 1 s were significantly higher during the fluticasone period (1,207 +/- 10 ml; 95% confidence interval, CI, 1,187-1,227 ml) compared to the placebo period (1,150 +/- 6 ml; 95% CI 1,138-1,162 ml; p = 0.0012). In conclusion, this n-of-1 RCT suggests the efficacy of high-dose inhaled fluticasone in our patient with lung transplant BOS. We propose to conduct a multicenter RCT of high-dose inhaled steroids. Until further data are available, this treatment modality should be offered to patients with lung transplant BOS.