BACKGROUND: Extracorporeal photopheresis (ECP) has been used to treat acute and chronic rejection after solid organ transplantation. However, data supporting the use of ECP for bronchiolitis obliterans syndrome (BOS) after lung transplantation is limited. METHODS: We retrospectively analyzed the efficacy and safety of ECP for progressive BOS at our institution. Between January 1, 2000, and December 31, 2007, 60 lung allograft recipients were treated with ECP for progressive BOS. RESULTS: During the 6-month period before the initiation of ECP, the average rate of decline in forced expiratory volume in 1 second (FEV(1)) was -116.0 ml/month, but the slope decreased to -28.9 ml/month during the 6-month period after the initiation of ECP, and the mean difference in the rate of decline was 87.1 ml/month (95% confidence interval, 57.3-116.9; p < 0.0001). The FEV(1) improved in 25.0% of patients after the initiation of ECP, with a mean increase of 20.1 ml/month. CONCLUSIONS: ECP is associated with a reduction in the rate of decline in lung function associated with progressive BOS.