The incidence of renal angiomyolipoma is increased in patients with tuberous sclerosis. Renal angiomyolipomas frequently exhibit both intratumoral and subcapsular or perirenal hemorrhage when they grow into the extrarenal space. Evidence of serial morphologic change is crucial to decision-making for surgical exploration in patients with growing renal angiomyolipomas. We report two cases of angiomyolipoma of the kidney with expansion of an angiomyolipoma into the subcapsular region. Neither patient had tuberous sclerosis and both developed bleeding when the mushroom-shaped tumor reached the extrarenal space. These cases suggest that expansion of the tumor into the subcapsular region is indicative of impending rupture of a renal angiomyolipoma.