OBJECTIVE: A retrospective study involving 13 institutions was performed to assess the efficacy of conversion from cyclosporine (INN: ciclosporin) to tacrolimus. METHODS: Data from 244 patients were analyzed. Indications for conversion were recurrent-ongoing rejection (n = 110) and stage 1 to 3 bronchiolitis obliterans syndrome (n = 134). RESULTS: The incidence of acute rejection decreased significantly within 3 months after versus before the switch from cyclosporine to tacrolimus (P <.01). For patients with recurrent-ongoing rejection, the forced expiratory volume in 1 second decreased by 1.96% of predicted value per month (P =.08 vs zero slope) before and increased by 0.34% of predicted value per month (P =.32 vs zero slope) after conversion (P <.06). For patients with stage 1 to 3 bronchiolitis obliterans syndrome, a significant reduction of rejection episodes was observed (P <.01). In single transplant recipients a decrease of the forced expiratory volume in 1 second averaged 2.25% of predicted value per month (P <.01 vs zero slope) before and 0.29% of predicted value per month after conversion. Corresponding values for bilateral transplant recipients were 3.7% of predicted value per month (P <.01 vs zero slope) and 0.9% of predicted value per month (P = 0.04 vs zero slope), respectively. No significant difference in the incidence of infections within 3 months before and after conversion was observed. CONCLUSIONS: Conversion from cyclosporine to tacrolimus after lung transplantation is associated with reversal of recurrent-ongoing rejection. Conversion for bronchiolitis obliterans syndrome allows short-term stabilization of lung function in most patients.