This research is being done to study the effects (good and bad) of taking CellCept based on blood concentrations versus taking a fixed dose of CellCept without measuring the blood concentration. CellCept is one of the three immunosuppressant drugs (drugs that suppress the immune system) which will be taken as part of this kidney transplant study. Cyclosporine or tacrolimus and corticosteroids are the two other drugs which will be taken.