Patients begin a mycophenolate mofetil (MMF)-containing regimen within the first 5 days after transplantation. Patients have blood drawn on postoperative days 7, 21, 42, 70, 98, 126, and 154. Urine is collected on postoperative days 7, 21, and 42. Patients with T-tube bile externalization also have bile collected on postoperative day 7.