Abstract : Peripheral nerve excitability is currently tested via the strength/duration curves, and by measuring the minimal intensity level (rheobase) of an efficient stimulation, and the minimal duration (chronaxy) for a stimulus equal to two times the minimal threshold. New 'threshold tracking techniques' were recently described (Bostock et al., 1991), which afford an automatic evaluation of nerve excitabilty. These methods investigate the mechanisms responsible for the membrane potential: passive ionic currents, activity of ionic pumps like the Na-K-ATPase; and the dynamic behaviour of large conductance sodium, potassium, and calcium channels, responsible for the generation and conduction of action potentials. Results obtained must however be evaluated taking into account the following items: stimulation is delivered through the skin and subcutaneous tissue; a nerve trunk is explored, and not a single fiber; most often the response is recorded over a muscle, hence through neuromuscular synapses