Thirty to forty years ago a group of diseases was described in which a hypochromic anemia occurred that did not respond to iron therapy. The anemia was attributed to disturbed iron utilization. It has later become evident that the common feature of this group of anemias is a disturbance of heme synthesis. Iron accumulates in the mitochondria of the nucleated red cells and characteristically I forms a ring of iron-staining granules surrounding the nucleus. There is hyperplasia of the nucleated red cells in the bone marrow, and siderosis is found in the liver and other organs. The picture resembles somewhat that produced by pyridoxine deficiency in experimental animals. This group of anemias was originally termed sideroachrestic anemia, but it is now more usually termed sideroblastic anemia. Both genetic and acquired forms are found.