 This open-label, 2-arm study will compare the pharmacokinetics of CellCept and mycophenolate sodium in kidney transplanted patients on a calcineurininhibitor-free mycophenolic acid-based therapy. On the study day patients will take their prescribed medication either CellCept or mycophenolate sodium. Blood samples will be drawn directly before and at intervals up to 12 hours after intake of the study medication. Anticipated time on study treatment is 12 hours and target sample size is 24. 