A patient with idiopathic sideroblastic anemia and atypical clinical and biochemical findings is described. He had a greatly increased erythrocyte and plasma protoporphyrin, but normal urine and fecal porphyrins. The erythrocyte protoporphyrin had a fluorescence spectrum typical of free protoporphyrin, but caused no photosensitivity. Bone marrow metal chelatase activity was normal. There were no clinical signs of liver disease. The abnormal porphyrin metabolism in this patient is not known though a number of explanations are discussed.