Tacrolimus has been effective both in primary and rescue therapy following steroid and OKT3-resistant acute rejection in liver and kidney transplantation. Due to the effects of tacrolimus on glucose metabolism, there has been concern about its use in simultaneous pancreas/kidney transplantation. We report on the results of six patients (three female, three male, age 35.2 +/- 7.3 years) converted from cyclosporin A to tacrolimus following simultaneous pancreas/kidney transplantation in steroid-resistant acute rejection. Tacrolimus was induced 2.8 +/- 1.7 months (range 1-4.8 months) after transplantation; follow-up was 3-18 months. Following conversion, creatinine levels declined in all patients [3.5 +/- 1.2 mg/dl before conversion, 3.0 +/- 1.9 mg/dl (n = 6) at three months, 1.4 +/- 0.1 mg/ dl at 1 year (n = 3)]. Before conversion, fasting blood glucose levels averaged 154 +/- 33 mg/dl, with three patients receiving insulin. Three months later no patient required insulin, the mean glucose level being 107 +/- 23 mg/dl (n = 6); at 1 year it was 92 +/- 9 mg/dl (n = 3). One patient lost his pancreatic graft after 4 months due to a mycotic aneurysm. We conclude that conversion to tacrolimus is a safe and effective treatment in cases of steroid-resistant rejections following pancreas/ kidney transplantation.