Tuberous sclerosis is a polymorphic, dominantly inherited syndrome caused by an inactivating mutation in a tumor suppressor gene. The disease involves benign tumors in several distinct organs such as the skin, kidneys, heart and central nervous system. The tumors interfere with organ function, but only some exhibit a significant tendency to grow. The clinical picture of tuberous sclerosis varies from nearly symptomless to a severe disease. Treatment of growing tumors associated with tuberous sclerosis is changing significantly, since their growth can be suppressed with rapamycin and its derivatives.