The validity of employing an equivalent symmetrical anode for expressing the space‐charge‐limited current between nonsymmetrical electrodes is examined. It is shown that when the equivalent anode is determined by the capacitance, the error in the expression for the current is usually quite small and its approximate magnitude may often be anticipated. Exact expressions for the capacitance of some basic electrode arrangements are given, followed by a brief resume´ of corrections required for interpretation of experimental data.