This paper is concerned with the interference between circuits in homogeneous cables, and its reduction. The line is replaced by its equivalent network, and, in the case of a four-wire group as used in superimposed circuits, the network consists of six members. The relations between the induced and inducing currents and voltages are established, and a quantitative definition of interference is given. The effects of unbalances in the line constants are discussed, and the influence of distance and frequency is investigated. An account is given of methods of measurement and of the means of reducing interference in cables, and a method developed by the author for dealing with the difficulties introduced by the distributed inductance in continuous loading is described.