F-wave main characteristics were investigated following stimulation of 8 different nerves (facial, axillary, radial, median, ulnar, femoral, deep peroneal, posterior tibial) in a population of normal healthy subjects. Additional studies compared different stimulation and recording techniques (stimulus intensity, stimulus duration, number of consecutive stimuli, facilitating maneuvers, type of recording electrodes). F-wave persistency varied markedly among the different nerves. Mean latencies were correlated to subjects' height, whereas conduction velocity was related to age. The optimal stimulation and recording parameters to obtain reliable information on F-wave studies were: stimulation duration of 0.2 msec with a strength adjusted 30% supramaximal to the direct M-response; administration of a train composed of 10 consecutive stimuli at rest and recording by concentric needle electrodes.