This paper presents an educational software tool with a user-friendly interface, which can be used for evaluation of available transfer capability (ATC). The software was developed using the MATLAB 1-2 software package. The software is designed for engineers who are involved in trading in electrical energy and for students (undergraduate and Master's) of Electrical Engineering who could, by using the software, gain a better insight into the theoretical knowledge and solve some practical engineering problems. ATC model limitations include the usual d.c. load fl ow inherent limitations as well as line thermal limits, prevalent in the literature on ATC. The structure and software capabilities are presented within the example of an ATC sensitivity study on a fi ve node/seven line transmission network, used for zonal market activities tests.