The paper develops a method for estimating the total intermodulation noise power falling into any channel in the transmission band of an a.m. multi-channel line system with many repeater sections in tandem. These sections may be composed of widely varying lengths of cable imperfectly equalized by non-identical amplifiers whose in-band feedback, output load impedance and output network response all vary with frequency. The whole system is loaded in such a way that the signal levels at each intermodulation source are also functions of frequency.After developing the basic theory, methods are given for estimating the system performance before building an amplifier and also when a model amplifier is available. These methods are more general than those previously published and are illustrated by examples.