The immunosuppressive agent tacrolimus is now widely used for the prevention of acute and chronic rejection in renal allograft recipients. We here report on three patients, who developed drug-induced fever due to tacrolimus one to five months after renal transplantation. Extensive search for a focus, autoantibodies and virus infection remained inconclusive. Therefore, drug-induced fever was suggested. After discontinuing tacrolimus and switching to cyclosporine A fever completely resolved within 24 h. This report demonstrates that tacrolimus-induced drug fever should be included in the differential diagnosis of fever of unknown origin in renal transplant recipients.