Protein and surfactant often occur together in various formulations of the chemical industry and are capable of modifying surfaces, altering colloid stability and controlling bulk viscosity. Protein Â surfactant interactions are expected to have significant structural consequences of solvent medium. In solution, proteins induce formation of surfactantmicelleswhich then bind to the polymer segments, leading to the formation of complexes. These complexes associate to form an insoluble phase which becomes soluble in the presence of excess of amphiphiles producing free micelles. The simultaneous presence of surfactants and proteins is required to achieve ideal dispersion effects inwhich surfactants provide emulsification capacity, interfacial tension control,whereas polymers impart colloidal stability and special rheological features. Thus, the practical importance of surfactant-(protein)polymer systems has motivated to carry studies of such systems, in which techniques such as viscosity and conductivity measurement, dialysis, fluorescence spectroscopy, NMR and neutron scattering have been used in order to explore the nature and kind of interactions present in these systems. These interactions are, of course characteristics of the protein and surfactant chosen. In the present studies, therefore, density and sound velocity of Triton X-100 (TX-100) in aqueous solutions of Lysozyme, which are sensitive to structural changes, have been measured over a wide temperature range (20-40oC). Molar volume (ï¦v) has been calculated from density measurements and various acoustical parameters such as apparent adiabatic compressibility (â) and apparent molar compressibility (ï¦k) have been calculated fromthe sound velocity data in order to account for the consequences of protein- surfactant interactions. Further information to this effect has been obtained by extending the work to include the viscositymeasurements as well. The activation energy parameter has also been calculated using viscosity values.