A detailed light scattering study of polystyrene (PS) in benzene solution at various scattering angles and PS concentrations has been carried out. The study includes static and dynamic light scattering measurements covering a dynamic range of 10(-6) to 10(2) s. The osmotic modulus of the polymer solution is measured as a function of polymer concentration by using the static light scattering technique. In the semidilute concentration regime, the homodyne intensity-intensity time correlation function deviates from a single exponential decay. The deviation was found to depend strongly on the polymer concentration. Angular-dependent measurements have facilitated the resolution of the time correlation function into a narrow cooperative diffusion mode and a broader slow component. At a large scattering vector, the slow component is found to be independent of the scattering angle. We have interpreted the experimental result in terms of the theory previously developed in this laboratory. We have attributed the slow component to the effect of viscoelasticity of the polymer solution. In addition, quasielastic light scattering studies of semidilute solutions of PS in mixed solvents consisting of benzene and diethyl phthalate with different values of the coupling parameter beta (defined in the text) have also been investigated. For the solutions with beta = 0, no viscoelastic component is observed in the QEL scattering spectrum, consistent with the theoretical prediction.