1. The limited bilirubin binding capacity of human serum albumin, and the fact that kernicterus can occur once the serum unconjugated bilirubin concentration exceeds this capacity, makes the assessment of non-albumin bound free bilirubin valuable in cases of severe neonatal hyperbilirubinemia. 2. Present methodology for this assessment utilizes Sephadex column chromatography, and is somewhat tedious and slow. 3. We have developed a procedure for assessing the albumin binding capacity of serum by titrating a sample of the serum with T-20 Dextran coated charcoal. 4. The method requires 2 ml of serum, takes 90 minutes to complete and is highly reproducible. 5. By this method, we can determine the reported secondary loose binding capacity of the albumin as well as the tight binding capacity which is determined by existing methods. 6. The tight binding capacity of a pool of normal adult human serum was found to be 20 mg/dl of serum. 7. This is in agreement with existing methods. The loose binding capacity was found to be an additional 10 mg/dl of serum. Added phenobarbital was found to lower the tight binding capacity, but not the secondary capacity.