Electrokinetic techniques can be used to gather specific information about concentrated dispersions such as electronic inks, mineral processing slurries, pharmaceutical products and biological fluids (eg blood). But, like most experimental techniques, intermediate quantities are measured, and consequently the method relies explicitly on theoretical modelling to extract the quantities of experimental interest. This talk will outline the application of a self-consistent cell-model theory of electrokinetics to the problem of determining the dielectric response of a dense suspension of spherical colloidal particles . The numerical predictions from the model will also be compared with published experimental results, with the model showing good agreement for the two measureable quantities . The high frequency behaviour of the system is also analysed using matched asymptotic techniques. This produces simple expressions for the limiting forms of the measureable quantities. The expression for the dynamic mobility is valid in the megahertz range, making it usiful in a laboratory situation .