Abstract A single-step isolation method for the glycoforms of human serum α 1-acid glycoprotein (AAG) using a hydroxylapatite column under a gradient elution program was developed. The concentrations of N-acetylneuraminic acid and monosaccharides (fucose, N-acetylglucosamine, galactose and mannose) of six AAG glycoforms were determined by the pulsed-amperometric detection method. For each AAG glycoform, significant sex-related differences in carbohydrate content have been observed only for AAG glycoforms two and six, and not for each AAG glycoform. The relationship between the extent of the branch in the glycan chain and the binding capacity to disopyramide were examined. Female AAG contained highly sialylated AAG glycoforms compared to male glycoforms. Conversely, male AAG was rich in the lower sialylated AAG glycoform. Furthermore, it was found that the drug binding capacity decreases with increasing branching of the glycan chain. This suggests that the binding sites of AAG are hindered by a relatively large carbohydrate moiety, such as tetraantennary structures.