A 19-year old patient with tuberous sclerosis presented with a renal angiomyolipoma. Because animal trials of tuberous sclerosis showed an effect of rapamycin on renal tumors, our patient was administered rapamycin for 6 months. During this time, the renal angiomyolipoma shrank significantly, regrew during an 8-month period, and decreased in size again after readministration of rapamycin.