The so‐called “auxilliary point” method for the interpretation of geoelectrical resistivity soundings has received considerable attention from the European geophysicists. However, almost no mention of it has been made in the American literature. It is the aim of this paper to introduce the method and to establish its mathematical relationship to the so‐called “Dar Zarrouk” parameters. The auxiliary point method is an empirical graphical method by which a multilayer problem is progressively reduced to the simple two‐layer case. Hence, to interpret a multilayer sounding curve, use is made of the available two‐ and three‐layer master curves in conjunction with one, or more, of four charts that represent families of auxiliary curves. The four charts are known as the Hummel (H‐chart), the Anisotropy (A‐chart), the Displaced‐Hummel (DH‐chart), and the Displaced‐Anisotropy (DA‐chart). The mathematical basis for the drawing of these charts is discussed, and furthermore the identity of the Dar Zarrouk point to the anisotropy point is shown. The relation between the various parameters of the auxiliary points and the Dar Zarrouk point is graphically illustrated. Other auxiliary methods for the interpretation of sounding curves, e.g., the Cagniard and the Ono charts are essentially the same as the auxiliary point charts. A theoretical four‐layer case illustrates the practical use of the method, its advantages, and its limitations.