A 38-year-old woman with type 1 diabetes underwent kidney-pancreas transplantation. Her postoperative course was complicated due to recurrent acute graft rejections and pancreatitis. After initial immunosuppression with microemulsion cyclosporine, mycophenolate mofetil, and prednisone with muromonab-CD3 induction, cyclosporine was switched to tacrolimus on day 44. The initial dosage was 5 mg twice/day, but it was gradually increased to 10 mg twice/day, aiming at 15-20 ng/ml. On day 17 of tacrolimus therapy the woman developed sudden hearing loss with tinnitus. The serum tacrolimus level was 28.3 ng/ml (therapeutic range 10-20 ng/ml) on day 20 of tacrolimus therapy, and peaked at 34.9 ng/ml on day 28. Two audiograms performed on days 28 and 29 confirmed bilateral hearing loss of 80% for speech perception, characterized as mild to moderate sensorineural hearing loss with speech reception threshold of 35 dB (normal < 20 dB) in both ears. The tacrolimus dosage was gradually reduced to 6 mg twice/day by day 36, with drug level 9.7 ng/ml, after which her hearing gradually recovered.