Binding of desialylated a1-acid glycoprotein by human liver particulate fraction exihibited a dependence on the presence of calcium chloride whereas Cu++, Mn++, Zn++ Fe++ and Co++ inhibited the binding. The other cations such as K+, Na+, Ba++, Mg++ or Pb++ were determined to be non-effective on the binding activity. The pH of the assay for binding was not critical in the range of 6.5 to 9.5. The binding process required the presence of terminal sialic acid on the particulate protein. Fifty nine per cent of binding activity in the original liver paticulate fraction were recovered in acetone powder. Extraction of the acetone powder with a buffer containing EDTA resulted in an increased total binding activity. After extraction with 1–10% Triton X-100, 60% of the activity were still detected in insoluble fraction.