An immune hemolytic anemia occurs in a few patients in whom the concentration of antibody on the red cell is below the level for detection by the usual antiglobulin test. Clinically, these patients are identical to patients with warm type Coombs-positive hemolytic anemia, except for the quantity of antibody on the cell. The course of the hemolytic disease is highly variable. It is postulated that the properties of the antibody in conjunction with the sensitivity of the reticuloendothelial system for antibody-coated cells account for hemolytic anemia occurring with such low concentrations of antibody. The response to steroid therapy and splenectomy, when indicated, is usually favorable.