In this article, we present a new network flow-tracing method. This new method is designed to trace flow paths across a network from selected consumers to a specified producer. Flow tracing gives fundamental insight into the relations between consumers and producers. The new method is based on a matrix calculation that considers the transmission losses in a simple way. We tested the new flow-tracing method on an 18-bus electric-power test system. Since all the transmission systems have some common characteristics, knowledge from one technical field can be imposingly used in the other fields. The idea is to spread the knowledge and to find some basic principles of observed phenomena enabling to solve problems in a proper manner. In this way, a better insight into the system operation and control can be obtained, especially nowadays when deregulation and liberalization of transmission systems are introduced. © 2004 Elsevier Ltd. All rights reserved.