Dynamic and static light scattering measurements have been made on lysozyme solutions at 25 degrees C in 0.1 M phosphate buffer, pH 6.88, in the presence of sodium dodecyl sulfate (SDS). The concentration of SDS has been varied over a wide range (0-0.2 g/ml). It is found that under these conditions both SDS micelles and lysozyme(Lys)-SDS complexes coexist. Addition of lysozyme at constant SDS concentration leads to formation of more lysozyme-SDS complex. The translational diffusion coefficient of the complex increases with SDS concentration. It is also found that two lysozyme molecules are associated in the protein-surfactant complex.