Experiments were conducted to investigate the Mn-Fe interrelationship in the chick. Graded levels of Fe and two levels of Mn were added to a corn-soybean meal diet (157 mg Mn/kg; 372 mg Fe/kg) and to an Fe-deficient casein-dextrose diet containing 15.4 mg Mn/kg and 5.0 mg Fe/kg. Dietary Fe had little effect on the Mn status of the chick, regardless of the level of Fe supplementation. Conversely, Mn supplemented at 1,000 mg/kg reduced blood hemoglobin concentration, but only when the dietary Fe level was at or below the chick's requirement. Levels of supplemental Fe up to 2,500 mg/kg had no effect on performance of chicks fed the corn-soybean diet, but a supplemental level of 5,000 mg Fe/kg diet reduced both weight gain and bone ash concentration. These data suggest that the interaction between Mn and Fe in the chick is a unidirectional phenomenon, in which excess Mn impairs Fe utilization but excess Fe does not antagonize Mn.