Two randomized controlled trials of mycophenolate mofetil (MMF) in the treatment of myasthenia gravis (MG) were recently completed. Although neither study demonstrated efficacy of MMF in the population of patients studied, there are valuable lessons in the way these studies were developed and performed. After reviewing the design and results of these trials, we discuss possible reasons leading to negative results and the lessons learned, which should be useful for future clinical trials in MG.