Therapy with tacrolimus has been proven effective in patients with steroid-resistant rejection episodes. It was the objective of the present study to evaluate the efficacy of tacrolimus in patients with long-lasting primary or secondary non-function (defined as being on dialysis for at least 28 days) converted for biopsy proven acute rejection and to determine parameters of prognostic value. Eight patients with biopsy proven acute interstitial rejection unsuccessfully treated with steroids were converted from a cyclosporine based immunosuppressive regimen to tacrolimus. Three patients were additionally pretreated with OKT3 without success. The tacrolimus whole blood through level was 7.5 +/- 2.6 ng/ml at one week and 8.1 +/- 3.4 ng/ml at one month after conversion. The follow-up period after conversion to tacrolimus ranged from 12-18 months. In four patients hemodialysis was stopped after 78 +/- 49 days (range 36-145 days). One year thereafter, creatinine was 3.9 +/- 2.7 mg/dl. In conclusion, our observations, although obtained in a small number of patients, offer some hope in this selected group and may encourage further studies in patients with long-term dialysis after renal transplantation.