A comparison between experimental measurements and theoretical calculations of the permittivity and conductivity of concentrated colloidal suspensions is presented. Dielectric spectroscopy measurements for 100 nm and 200 nm diameter polystyrene spheres at volume fractions between phi = 0.01 - 0.18 and electrolyte concentrations 0.01-1 mM KCl (P.J. Beltramo, E.M. Furst, Langmuir 28 (2012) 10703-10712) are compared to cell-model calculations that account for the hydrodynamic and electrokinetic interactions between particles (F. Carrique, F.J. Arroyo, M.L. Jimenez, A.V. Delgado, J. Chem. Phys. 118 (2003) 1945-1956). Under most conditions, there is good agreement between experiment and theory. At low ionic strengths, the dielectric increment exhibits a low-frequency plateau in the experimental spectroscopy and cell model calculations. However, at the highest ionic strengths, the cell model predicts a low frequency plateau that is not observed experimentally. The conductivity increments qualitatively agree over all volume fractions, ionic strengths and frequencies. (C) 2013 Elsevier Inc. All rights reserved.