Mycophenolate mofetil is the semisynthetic morpholinoethyl ester of mycophenolate acid, which has been developed as an immunosuppressive agent to prevent rejection of transplanted organs. It was commercialized as CellCept by Hoffmann-La Roche. Mycophenolic acid was originally used to treat psoriasis in the 1970s. More recently, this agent has been used to treat several inflammatory conditions including systemic lupus erythematosus, particularly in lupus nephritis. Currently it is in clinical trials for autoimmune myasthenia gravis, which will be the focus of this article, although the knowledge of clinical pharmacology and safety of this drug is based on use in transplant patients, the only approved use.