Electroviscous effects of dilute sodium poly(styrenesulfonate) solutions subject to a simple shear flow are studied experimentally. Emphasis is placed on investigation of the coupled primary and tertiary effects using different added salt species. At constant shear rate, the intrinsic viscosity is found to be in descending order for solutions with added LiCl, NaCl, and KCl at equal molar concentration. A similar descending order is also observed for MgCl2, CaCl2, and BaCl2. The noticeable difference in the intrinsic viscosity between various added salts indicates that the primary effect associated with distortion of the electric double layer caused by the imposed flow cannot be neglected. The experimental data also show that the intrinsic viscosity of a solution with added divalent cations is lower than that with monovalent ones at constant ionic strength.