Standard cyclosporine-based immunosuppression is ineffective in the treatment of refractory acute rejection (RAR) and obliterative bronchiolitis (OB) that follows lung transplantation. The aim of this study was to evaluate the results of switching from cyclosporine to tacrolimus in the treatment of these situations. Nineteen patients entered the study. The indication for switching was OB in 11 patients and RAR in 8. Mean age was 41.3 +/- 13.1 years. In patients with RAR, the number of acute rejections was 1.5 +/- 0.7 and there were zero episodes per patient per 100 days before and after switching, respectively ( P = 0.02). There was no significant reduction of the decline of forced expiratory volume (FEV(1)) within 6 months after switching in patients with OB. We conclude that the conversion from cyclosporine to tacrolimus was associated with favourable results in the treatment of RAR. Further studies are required to assess the influence of this approach in the treatment of OB.