The relationship between regional reproduction rates of bald eagles (Haliaeetus leucocephalus) and concentrations of p,p′-dichlorodiphenyldichloroethylene (p,p′-DDE) and total polychlorinated biphenyls (PCBs) in blood plasma from nestling bald eagles was assessed. Blood was analyzed from 309 nestlings from 10 subpopulations of eagles across the Great Lakes region. Geometric mean concentrations of p,p′-DDE and total PCBs were inversely correlated to the productivity and success rates of nesting bald eagles within nine subpopulations. Nestlings eight weeks of age and older had significantly greater geometric mean concentrations of total PCBs and p,p′-DDE than nestlings less than eight weeks of age. The ability to use measurements of p,p′-DDE and total PCBs in nestling blood to determine the potential impact of these contaminants on adult nesting on a regional scale was demonstrated.