Anthramycin methyl ether (AME) was tested for its ability to suppress erythropoiesis in the mouse. AME was injected either subcutaneously or intraperitoneally in doses ranging from 0.2 to 1.0 mg/kg. Radioiron was injected intravenously at varying times after AME and the 48-hour uptake in peripheral erythrocytes was determined. When subcutaneous injections were used, a threshold dose of greater than 0.2 mg/kg was required to reduce the uptake of radioiron. Maximum suppression was noted at 1.0 mg/kg AME. Intraperitoneal injections were more effective than subcutaneous ones; a maximum suppression was noted after 0.6 mg/kg. The nadir of radioiron incorporation was noted between 24 and 48 h after AME (1.0 mg/kg, s. c.) injection. Recovery required 10–12 days after which a slight overshoot above 59Fe incorporation in normal mice was observed.