Background We conducted a placebo-controlled trial of azithromycin therapy in bronchiolitis obliterans syndrome (BOS) post lung transplantation. 12?weeks. Study Completers showed an estimated mean difference in FEV1 between treatment groups (azithromycin minus placebo) of 0.278?L, with 95% CI for the mean difference: 0.170?L to 0.386?L (p=