Upon arrival at the Clinical Center a catheter is inserted into the subject's arm vein. At 7:00 AM, the subject takes one dose of MMF by mouth with a glass of water. Small blood samples are collected through the catheter before the MMF dose and again at 0.5, 1, 1.5, 2, 3, 4, 6, 8, 10, and 12 hours after taking the drug. Heart rate and blood pressure are measured before the blood collection and then every 4 hours. After the last blood sample is collected, the volunteer can return home.