The theory developed by Watterson and White (Watterson, I. G., and White, L. R., J. Chem. Sec, Faraday Trans. 2 77, 1115 (1981)) to calculate the primary electroviscous coefficient of a suspension of charged spherical colloidal particles has been extended, by considering the presence of a dynamic Stern layer onto the particle surface, following the method developed by Mangelsdorf and White (Mangelsdorf, C. S., and White, L. R., J. Chem Sec. Faraday Trans. 80, 2859 (1990)) for electrophoresis. The presence of mobile ions causes the primary electroviscous coefficient to decrease compared to when the Stern layer ions are inmobile. A separate dependence of the primary electroviscous coefficient on kappa(-1) (Debye length) and a (particle radius) has been found.