Among neural lesions of the arms, the most common one is the medianus lesion in the carpal tunnel, followed by the ulnar nerve lesion in the elbow, while the ulnar nerve compression in the Guyon tunnel is found rarely. Besides the history and the clinical picture, the electromyoneurographic analyses make an early and accurate diagnosis possible. The characteristics of the evoked muscle potential and distal latencies in the diagnosis of the carpal tunnel syndrome are of utmost importance. In diagnosing the cubital syndrome, the multisegmental determination of the motor conduction velocity of the ulnar nerve and the features of the M-potential obtained by means of stimulation above the compression are very important. Generally speaking, the slowing down of the motor conduction velocity remains localised to the entrapped segments. The neural potential over the compression in the elbow cannot be evoked, and it is hardly evoked in the wrist. Within the period of the last five years, the author examined 154 patients clinically and electrophysiologically. 132 had the carpal tunnel syndrome, 20 the ulnar groove syndrome, and 2 Guyon's canal syndrome. The patients were treated conservatively and operatively. The success in the conservative treatment of the carpal tunnel syndrome was evident in the first three months by the absence of sensory symptoms in more than 50% of cases. The constant effect was achieved after six months. In that period the EMG findings were not essentially changed, and motor symptoms were also stationary. With the operative treatment the unpleasant symptoms, pain and shudder, disappeared after a relatively short period. Definitive results were achieved after six months. Motor symptoms were less improved and the EMG findings were showing a tendency to improvement. The ulnar groove syndromes were not remarkably influenced by the conservative therapy. Half the operated patients lost their sensory symptoms. Within six months the other half remained with the same or even more trouble.