A fault is located along a telecommunications line between the network terminating equipment and the local exchange by measuring a change in the capacitance of the line when compared with the capacitance under normal operating conditions. A geographical information system is used to plot all possible routes for the line between the terminating equipment and the exchange, and the most probable route is selected based on the known positions of nodes along the line, such as pole mounted distribution points and streetside cabinets. The distance of the fault along the line is then plotted along the most probable route to determine an accurate fault location, which is given to a field technician as the location of the nearest premises or a grid reference.