The present report describes what is probably the largest single-centre experience in Switzerland in treating recurrent, antibody-resistant or chronic rejection in kidney transplant patients by switching the patients from ciclosporin-based immunosuppression to tacrolimus. Thirty-eight patients, who received transplants in Basle and follow-up in Basle and Aarau, were switched from ciclosporin to tacrolimus-based immunosuppression between 1993 and the end of 1996 and followed up for at least six months. The initial median dose of tacrolimus was 0.21mg/kg/day, given in two divided doses, 12h after the last dose of ciclosporin. Graft survival in this high-risk group of patients was 70% at one year after transplantation. The most significant side effect was persistent diabetes mellitus in 16% of the patients. Renal function, which initially worsened in the tacrolimus patients, improved over time. Gingival hyperplasia and hypertrichosis, which are often associated with ciclosporin therapy, were not observed in the tacrolimus patients. Mycophenolate mofetil (MMF), combined with tacrolimus provided no additional benefit for the patients. In 14 of 20 patients on combination therapy, MMF had to be withdrawn due to gastrointestinal side effects.