Mycophenolate mofetil (MMF) has become a standard component of immunosuppressive regimens in adult and pediatric renal transplantation. Especially in children, MMF is known to have clinically obvious gastrointestinal side effects such as diarrhea or abdominal pain that can be dose-limiting or require drug discontinuation. In contrast, we report isolated weight loss unaccompanied by obvious clinical gastrointestinal symptoms in two pediatric renal transplant patients taking MMF. Both patients began gaining weight again after conversion to azathioprine. Accordingly, subspecialists and generalists caring for pediatric kidney transplant recipients taking MMF should be aware of this clinically "silent" complication.