Bovine beta-lactoglobulin (BLG) has two genetic variants known as BLG A and B. The interaction of sodium n-dodecyl sulphate (SDS) with its two variants has been studied by different experimental techniques such as titration microcalorimetry, equilibrium dialysis, UV spectrophotometry, and temperature scanning spectroscopy in acetate buffer at pH 3.2 and 25 degrees C. The binding data have also been interpreted in terms of structural points using the Wyman theoretical model. The results from different techniques show that BLG B has greater thermodynamic stability than BLG A.