16 patients suffering from syringomyelia were checked for additional peripheral nerve lesions. On voluntary effort, often in conformity with the decrease of muscle strength, a moderate rarefication of the discharge patterns was apparent. Fasciculation potentials were common. Motor conduction velocities of the median and ulnar nerve were in the normal range in cases without additional peripheral nervous lesion at the elbow or the carpal. Depending on the severity of the peripheral nervous lesion, we found the duration of the muscle action potentials increased.