Dynamic light scattering (DLS) and static light scattering (SLS) were used to characterize the structure and dynamics of solutions of polystyrene of molecular weight 390 000 in 1,1,2,2-tetrachloroethane. Mutual diffusion coefficients were determined as functions of concentration and temperature. The diffusion virial coefficients were determined and compared to several theoretical predictions. The DLS intensity autocorrelation function was also carefully examined for the possible presence of fast modes in order to provide a comparison to polystyrene studied in ternary solutions including a rodlike polymer (paper 2).