Angiofibromas from two patients with tuberous sclerosis were studied by light and electron microscopy. Light microscopy revealed that these tumor-like nodules (which in the past have been called adenoma sebaceum) were made up of dilated capillaries, venules and arterioles embedded in connective tissue. At the ultrastructural level the arterioles embedded in connective tissue. At the ultrastructural level the endothelium of these vessels showed large numbers of microvilli on their luminal surface. The stroma contained many banded structures (so-called fibrous long spacing collagen). Myofibroblasts recently described in juvenile nasopharyngeal angiofibromas were not found in these angiofibromas of tuberous sclerosis.