The bilirubin (BR)-binding capacity of albumin in serum from cord blood, as estimated by Sephadex gel filtration, is less than that of adult serum. The binding site at which BR is tightly bound by albumin in pools of infant serum was saturated at an average BR/albumin molar ratio of 0.66, while in adult serum the ratio was 1.00. With further increase in BR concentration, albumin of infant serum bound BR less than that of adult serum. These findings appear to have clinical significance with respect to the danger of BR encephalopathy in icteric infants.