A method and system for evaluating the current-voltage characteristics of devices where negative resistance behavior is observed. More particularly the present invention relates to a method and system for evaluating accurately the electrical overstress or ESD performance of semiconductor devices during the voltage transition region (positive to negative). The method comprises applying a signal comprising at least two amplitudes within the pulse. By suitably adjusting the amplitude of the first level, such that it is high enough to trigger the device-under-test, and subsequently applying one or more levels within the same signal while keeping the device-under-test in the on-state, the device IV characteristics can be comprehensively extracted, without being limited by the system loadline. The method may use a rectangular pulse testing set-up, also known as transmission line measurement set-up, with a single loadline characteristic to determine a portion or the complete ESD characteristic of the device-under test.