The binding properties of Sudlow's site-specific drugs to glycosylated bovine serum albumin (G-BSA) (1.25 mol glucose per mol of albumin) have been investigated using the circular dichroism (CD) method. Site I-specific drugs, phenylbutazone and warfarin, and site II-specific drugs, flufenamic acid and ibuprofen, were used. The induced ellipticities of phenylbutazone, flufenamic acid and ibuprofen-G-BSA complexes diminished and those of warfarin complex were enhanced in comparison with those for the intact bovine serum albumin (BSA) complexes. These CD change suggests that the glycosylation of BSA at the primary modification site influences the binding properties of the site-specific drugs to serum albumin.