We are reporting a case of generalized nevus anemicus in an adult, which was not associated with phacomatosis or pheochromocytoma. The pharmacological investigation of the vasomotricity showed permanent vasoconstriction in the anemic areas. The cutaneous levels of catecholamines were seven times as high in the anemic areas as in the sound areas. We have investigated a possible increase in the number of APUD by a histochemical method (Grimelius’s stain). This possible increase might have accounted for a local hypersecretion of catecholamines. Our investigation was negative. No etiological mechanism can be suggested.