Short-term improvement in lung function was observed in 5 of 6 lung transplant recipients with bronchiolitis obliterans syndrome (BOS) who were treated with oral azithromycin. We assessed the long-term effect (mean duration 10 months) of treatment with oral azithromycin in 11 lung transplant recipients with BOS. Mean forced expiratory volume in 1 second (FEV1) was 40 +/- 9% at initiation of azithromycin treatment, 39 +/- 10% after 1 month, 39 +/- 12% after 4 months, 38 +/- 10% after 7 months and 38 +/- 10% after 10 months, respectively (statistically non-significant for all data). We conclude that long-term administration with oral azithromycin does not reverse BOS in lung transplant recipients, but may slow progression of the disease.