In light-exposed areas of the skin patients with erythropoietic protoporphyria show deposits of a hyaline material around the capillaries of the upper dermis. Histochemically this material is PAS-positive and – by electron microscopy – reveals a finely fibrillar ultrastructure. The basal laminae of the small vessels are found to be multiplied and often show continuity with and transitional stages to the fibrillar masses. Basal Laminae and fibrillar masses are of the same ultrastructure. The perivascular deposits are supposed to represent material of excessively synthesized basal laminae of endothelial cells containing transuded substances as well as degenerative products of collagen.