Lung transplantation is a life saving procedure for patients with a terminal lung disease such as cystic fibrosis. Approximately, one in 3,500 children in the United States are born with cystic fibrosis each year with the predicted survival reaching 36.9 years in 2006. Cystic fibrosis was the third lead indication for lung transplantation in 2006. Cystic fibrosis is a genetic disease that can affect the way the body can remove salt from various organs. It results in mucus blocking the ducts of the lungs and pancreas leading to inability to handle oxygen and malabsorption of nutrients. Malabsorption is a common complication of cystic fibrosis that can affect the way the anti-rejection medications are absorbed. One medication that is utilized after transplant to prevent rejection is mycophenolate mofetil. This medication may not be absorbed adequately in this population due to their disease thus placing these patients at increased risk of rejection. At the investigators' institution, all transplant patients are initiated at the same mycophenolate dose regardless of their underlying disease. The limited available literature regarding cystic fibrosis transplant patients and mycophenolate suggests that these patients require higher doses due to their erratic absorption. The purpose of this study is to evaluate the effects of mycophenolate mofetil on the body in lung transplant patients who have cystic fibrosis in efforts to improve survival outcomes.