Since the early discovery of H-reflex by Hoffmann in 1918 there have been a great number of articles in the literature suggesting its clinical used by Magladery in the early 1950. Our experiments about measurement of latent time in H-reflex were performed on 40 normal male adult(composed of medicos and medical officers) and 82 patients(lumbago 40, lumbar disc 42) admitted at CAFGH from January '79. to August '79. The result about normal adult are as follows: 1) The mean value and the standard deviation of the latent time in normal adult(height 171+/-5.14 cm) is 27.74+/-1.86 msec at right leg, 27.77+/-1.64 msec at left one respectively. 2) There may be a linear relationship between latency and the height of normal adult and the difference between right and left is revealed 0.15+/-0.19 msec. We compare the measurementon the 82 patients group with the normal adult experimental groups in addition literatures review.