For the accurate prediction of the performances of saturated synchronous machines, the saturation characteristics in both the direct and quadrature axes are needed. The d-axis saturation characteristic of a synchronous machine can be measured easily by the open-circuit test with the machine excited from its field winding. On the other hand, the q-axis saturation characteristic of a synchronous machine cannot be measured applying a similar easy, simple method and, as a result, these characteristics are usually not experimentally measured and are not available. In this paper, three possible experimental methods for determining the q-axis saturation characteristics of both cylindrical-rotor and salient-pole synchronous machines are presented. The merits and demerits of these experimental methods are discussed from the point of view of their complexity and their accuracy. Comparisons between the measured q-axis saturation characteristics obtained by these experimental methods are made for a cylindrical-rotor machine and two salient-pole machines. Moreover, the various sources of errors, which may affect the accuracy of determining the q-axis saturation characteristics by these methods, are investigated.