Amyotrophic lateral sclerosis (A.L.S.) is not only the most common form of disease restricted to the motor neurons, but also involves both the upper and lower motor neurons. Electromyography(EMG), as an extension of clinical examination, is the simple and commonly used test in evaluation of lower motor neuronal diseases.

The authors performed nerve conduction study and needle electromyography in 13 cases A.L.S., in dept of rehabilitation medicine in Kang Nam St. Mary's Hospital, Catholic Medical College, from Jan. 1982 to Aug. 1984.

The results were as follows.

1) Slow conduction velocity or no response of median and peroneal motor nerves were in 38.5% and 23.1%, respectively.

2) Normal values of sensory nerve conduction study.

3) Positive sharp waves and fibrillations were found in all case, but fasciculations and complex repetitive discharges can be seen in 9 cases(69.2%), and 3 cases(23.1%), respectively.

4) Tongue fasciculations were showed more frequently in patients with clinical bulbar symptoms than in cases without these symptoms.

5) Number of motor unit action potentials was decreased in all cases, but amplitude and duration of each motor unit action potentials were increased as well as proportion of polyphasic potentials in 5 cases, respectively.