The effect of binding and conformational changes induced by anionic surfactants sodium dodecyl sulfate (SDS) and sodium octyl sulfate (SOS) on bovine serum albumin (BSA) have been studied using differential scanning calorimetry (DSC), circular dichroism (CD), fluorescence and UV spectroscopic methods. The denaturation temperature, van't Hoff enthalpy and calorimetric enthalpy of BSA in the presence of SDS and SOS and urea at pH 7 have been determined. The results indicate that SDS plays two opposite roles in the folding and stability of BSA. It acts as a structure stabiliser at a low molar concentration ratio of SDS/BSA and as a destabilizer at a higher concentration ratio as a result of binding of SDS to denatured BSA. The Brandts and Lin model has been used to simulate the results.