Spinal evoked potentials were recorded at the T12-L1 interspinous vertebral level with a standard monopolar EMG needle stimulating the posterior tibial nerve. In and average height adult, this level usually represents the nerve root's spinal cord entry for the posterior tibial nerve.

We studied the spinal evoked responses in 46 normal adults, mean age 29.31±6.03 years with range of 19-46 years.

The results were summarized as follows:

1) The potential was most consistent and reporoducible at the frequency filter bandwidth of 100-750 Hz.

2) The mean value of N1 latency and amplitude of potentials with the frequency band at 100-750 Hz was 19.53±0.76 msec and 2.30±1.46 uV, respectively.

3) There was a significant correlation between the delay of the N1 latency and the increase of subjects' height.

4) The mean N1 latency with the high frequency filter constant at 750Hz varying the low frequency filter 10 Hz to 100 Hz tended to decrease mildly but the amplitude decreased markedly.

5) The mean N1 latency with the low frequency filter constant at 10Hz varying the high frequency filter from 3000 to 500 Hz tended to increase, without significant change in amplitude.