At our institution, CF patients are managed the same as any other lung transplant patients in regards to immunosuppression. Standard starting dose for MMF is 1000mg twice daily within our institution, and pre-dose MPA levels are not routinely measured since they do not reflect MPA exposure. In contrast, other transplant centers dose MMF higher in CF patients based on the limited reports above. The purpose of this study is to determine PK of MPA and MPAG in CF patients on tacrolimus and compare them to a cohort of non-CF lung transplant patients.