Electrophoretic mobility of a kaolinite suspension expressed as a zeta potential using the Smoluchowsky formula. The dashed curve represents the prediction according to the standard theory. In this article a new formula for the electrophoretic mobility of a spheroidal colloid is given. This formula and the formula presented in Chassagne and Bedeaux C. Chassagne, D. Bedeaux, J. Colloid Interface Sci. 326 (2008) 240–253 for the dipolar coefficient of a spheroidal colloid are intertwined. The combination of electrophoresis and complex conductivity measurements (from which the dipolar coefficient can be derived) allows to assess both the zeta potential and the Stern layer conductance. We will in particular show that the values found for the zeta potential from both techniques are similar in the case of the kaolinite suspension studied. Electrophoretic mobility data are also presented and discussed for a wide range of ionic strengths, different types of salt and various pH. This data has been used in flocculation studies on the same kaolinite samples F. Mietta, C. Chassagne, J.C. Winterwerp, J. Colloid Interface Sci., accepted for publication, doi:10.1016/j.jcis.2009.03.044.